diff --git a/app.js b/app.js
index d90bc41..a1a7859 100644
--- a/app.js
+++ b/app.js
@@ -1,8 +1,8 @@
-var themeMod = require('./utils/theme')
+const themeMod = require('./utils/theme')
 
 App({
-  onLaunch: function () {
-    var settings = wx.getStorageSync('user_settings')
+  onLaunch() {
+    const settings = wx.getStorageSync('user_settings')
     if (!settings) {
       wx.setStorageSync('user_settings', {
         planId: 'beginner',
@@ -12,7 +12,7 @@ App({
         vibrate: true
       })
     }
-    var streak = wx.getStorageSync('current_streak')
+    const streak = wx.getStorageSync('current_streak')
     if (!streak) {
       wx.setStorageSync('current_streak', { count: 0, lastDate: '' })
     }
diff --git a/components/calendar-heatmap/calendar-heatmap.js b/components/calendar-heatmap/calendar-heatmap.js
index 350df6a..e81d55c 100644
--- a/components/calendar-heatmap/calendar-heatmap.js
+++ b/components/calendar-heatmap/calendar-heatmap.js
@@ -1,4 +1,4 @@
-var util = require('../../utils/util')
+const util = require('../../utils/util')
 
 Component({
   properties: {
@@ -12,70 +12,63 @@ Component({
   },
 
   observers: {
-    'year, month, records': function (year, month, records) {
+    'year, month, records'(year, month, records) {
       this._compute(year, month, records)
     }
   },
 
   lifetimes: {
-    ready: function () {
-      this._compute(this.properties.year, this.properties.month, this.properties.records)
+    ready() {
+      const { year, month, records } = this.properties
+      this._compute(year, month, records)
     }
   },
 
   methods: {
-    _compute: function (year, month, records) {
-      var weeks = util.getMonthCalendar(year, month)
-      var recordMap = {}
+    _compute(year, month, records) {
+      const weeks = util.getMonthCalendar(year, month)
+      const recordMap = {}
       if (records && records.length) {
-        records.forEach(function (r) {
-          var d = parseInt(r.date.split('-')[2])
+        records.forEach((r) => {
+          const d = parseInt(r.date.split('-')[2])
           recordMap[d] = (recordMap[d] || 0) + r.duration
         })
       }
 
-      var data = weeks.map(function (week) {
-        return week.map(function (day) {
+      const data = weeks.map((week) =>
+        week.map((day) => {
           if (!day) return null
-          var duration = recordMap[day] || 0
-          var color = 'transparent'
+          const duration = recordMap[day] || 0
+          let color = 'transparent'
           if (duration > 0) {
             if (duration < 30) color = '#FFE0D0'
             else if (duration < 60) color = '#FFB088'
             else if (duration < 120) color = '#FF6B35'
             else color = '#E05520'
           }
-          return { day: day, duration: duration, color: color }
+          return { day, duration, color }
         })
-      })
+      )
 
       this.setData({ weeks: data })
     },
 
-    onDayTap: function (e) {
-      var day = e.currentTarget.dataset.day
+    onDayTap(e) {
+      const day = e.currentTarget.dataset.day
       if (!day) return
-      var cell = null
-      var weeks = this.data.weeks
-      for (var i = 0; i < weeks.length; i++) {
-        for (var j = 0; j < weeks[i].length; j++) {
-          var c = weeks[i][j]
-          if (c && c.day === day) { cell = c; break }
-        }
-        if (cell) break
-      }
+      const cell = this.data.weeks.flat().find(c => c && c.day === day)
       if (!cell || cell.duration <= 0) return
       this.triggerEvent('daytap', {
         year: this.properties.year,
         month: this.properties.month,
-        day: day,
+        day,
         duration: cell.duration
       })
     },
 
-    getHeatColor: function (cell) {
+    getHeatColor(cell) {
       if (!cell || cell.duration <= 0) return 'transparent'
-      var d = cell.duration
+      const d = cell.duration
       if (d < 30) return '#FFE0D0'
       if (d < 60) return '#FFB088'
       if (d < 120) return '#FF6B35'
diff --git a/components/progress-ring/progress-ring.js b/components/progress-ring/progress-ring.js
index db48536..22da2b4 100644
--- a/components/progress-ring/progress-ring.js
+++ b/components/progress-ring/progress-ring.js
@@ -1,4 +1,4 @@
-var util = require('../../utils/util')
+const util = require('../../utils/util')
 
 Component({
   properties: {
@@ -17,8 +17,8 @@ Component({
   },
 
   observers: {
-    'remaining, status, duration, size, ringWidth, primaryColor': function () {
-      var texts = { idle: '准备开始', running: '坚持住', paused: '已暂停', completed: '完成!' }
+    'remaining, status, duration, size, ringWidth, primaryColor'() {
+      const texts = { idle: '准备开始', running: '坚持住', paused: '已暂停', completed: '完成!' }
       this.setData({
         displayTime: util.formatTime(this.data.remaining),
         statusText: texts[this.data.status] || ''
@@ -28,45 +28,40 @@ Component({
   },
 
   lifetimes: {
-    ready: function () {
-      var self = this
-      var query = this.createSelectorQuery()
+    ready() {
+      const query = this.createSelectorQuery()
       query.select('#ringCanvas')
         .fields({ node: true, size: true })
-        .exec(function (res) {
+        .exec((res) => {
           if (!res || !res[0] || !res[0].node) return
-          var canvas = res[0].node
-          var dpr = wx.getSystemInfoSync().pixelRatio || 2
-          var displaySize = self.data.size
+          const canvas = res[0].node
+          const dpr = wx.getSystemInfoSync().pixelRatio || 2
+          const displaySize = this.data.size
           canvas.width = displaySize * dpr
           canvas.height = displaySize * dpr
-          self._ctx = canvas.getContext('2d')
-          self._dpr = dpr
-          self._draw()
+          this._ctx = canvas.getContext('2d')
+          this._dpr = dpr
+          this._draw()
         })
     }
   },
 
   methods: {
-    _draw: function () {
-      var ctx = this._ctx
+    _draw() {
+      const ctx = this._ctx
       if (!ctx) return
 
-      var size = this.data.size
-      var dpr = this._dpr
-      var ringWidth = this.data.ringWidth
-      var duration = this.data.duration
-      var remaining = this.data.remaining
-      var primaryColor = this.data.primaryColor
+      const { size, ringWidth, duration, remaining, primaryColor } = this.data
+      const dpr = this._dpr
 
-      var w = size * dpr
-      var h = size * dpr
+      const w = size * dpr
+      const h = size * dpr
       ctx.clearRect(0, 0, w, h)
 
-      var cx = w / 2
-      var cy = h / 2
-      var radius = (size - ringWidth) / 2 * dpr
-      var lw = ringWidth * dpr
+      const cx = w / 2
+      const cy = h / 2
+      const radius = (size - ringWidth) / 2 * dpr
+      const lw = ringWidth * dpr
 
       // track ring
       ctx.beginPath()
@@ -76,11 +71,11 @@ Component({
       ctx.lineCap = 'round'
       ctx.stroke()
 
-      // progress arc (clockwise from 12 o'clock, represents remaining time)
-      var ratio = duration > 0 ? Math.max(0, Math.min(1, remaining / duration)) : 0
+      // progress arc (clockwise from 12 o'clock)
+      const ratio = duration > 0 ? Math.max(0, Math.min(1, remaining / duration)) : 0
       if (ratio > 0.001) {
-        var startAngle = -Math.PI / 2
-        var endAngle = startAngle + ratio * Math.PI * 2
+        const startAngle = -Math.PI / 2
+        const endAngle = startAngle + ratio * Math.PI * 2
         ctx.beginPath()
         ctx.arc(cx, cy, radius, startAngle, endAngle)
         ctx.strokeStyle = primaryColor
diff --git a/custom-tab-bar/index.js b/custom-tab-bar/index.js
index 7e8ec76..f306460 100644
--- a/custom-tab-bar/index.js
+++ b/custom-tab-bar/index.js
@@ -1,4 +1,4 @@
-var themeMod = require('../utils/theme')
+const themeMod = require('../utils/theme')
 
 Component({
   data: {
@@ -7,23 +7,23 @@ Component({
   },
 
   lifetimes: {
-    attached: function () {
-      var theme = themeMod.getCurrentTheme()
+    attached() {
+      const theme = themeMod.getCurrentTheme()
       this.setData({ themeStyle: themeMod.getThemeStyle(theme) })
     }
   },
 
   pageLifetimes: {
-    show: function () {
-      var theme = themeMod.getCurrentTheme()
+    show() {
+      const theme = themeMod.getCurrentTheme()
       this.setData({ themeStyle: themeMod.getThemeStyle(theme) })
     }
   },
 
   methods: {
-    switchTab: function (e) {
-      var index = e.currentTarget.dataset.index
-      var pages = [
+    switchTab(e) {
+      const index = e.currentTarget.dataset.index
+      const pages = [
         '/pages/index/index',
         '/pages/records/records',
         '/pages/settings/settings'
diff --git a/pages/index/index.js b/pages/index/index.js
index d5e2a7a..debbcd8 100644
--- a/pages/index/index.js
+++ b/pages/index/index.js
@@ -1,7 +1,7 @@
-var storage = require('../../utils/storage')
-var planMod = require('../../utils/plan')
-var util = require('../../utils/util')
-var themeMod = require('../../utils/theme')
+const storage = require('../../utils/storage')
+const planMod = require('../../utils/plan')
+const util = require('../../utils/util')
+const themeMod = require('../../utils/theme')
 
 Page({
   data: {
@@ -22,38 +22,33 @@ Page({
     customInput: ''
   },
 
-  onLoad: function () {
+  onLoad() {
     this.refresh()
   },
 
-  onShow: function () {
+  onShow() {
     themeMod.applyThemeToPage(this)
     try {
-      var tb = this.getTabBar()
+      const tb = this.getTabBar()
       if (tb) tb.setData({ selected: 0 })
     } catch (e) {}
     this.refresh()
   },
 
-  onPullDownRefresh: function () {
+  onPullDownRefresh() {
     this.refresh()
     wx.stopPullDownRefresh()
   },
 
-  refresh: function () {
-    var settings = storage.getSettings()
-    var streak = storage.getStreak()
-    var todayRecord = storage.getTodayRecord()
+  refresh() {
+    const settings = storage.getSettings()
+    const streak = storage.getStreak()
+    const todayRecord = storage.getTodayRecord()
 
-    var records = []
-    var allRecords = storage.getRecords()
-    Object.keys(allRecords).forEach(function (key) {
-      records = records.concat(allRecords[key])
-    })
-
-    var plan = planMod.getPlan(settings.planId)
-    var planDay = planMod.getPlanDay(settings.planId, records)
-    var target = planMod.getTodayTarget(settings.planId, Math.min(planDay, plan.totalDays))
+    const allRecords = Object.values(storage.getRecords()).flat()
+    const plan = planMod.getPlan(settings.planId)
+    const planDay = planMod.getPlanDay(settings.planId, allRecords)
+    const target = planMod.getTodayTarget(settings.planId, Math.min(planDay, plan.totalDays))
 
     this.setData({
       todayTarget: target,
@@ -68,37 +63,37 @@ Page({
     })
   },
 
-  onStartTrain: function () {
+  onStartTrain() {
     wx.navigateTo({ url: '/pages/timer/timer' })
   },
 
-  onFreeTrain: function () {
+  onFreeTrain() {
     this.setData({ showPicker: true, customInput: '', customDuration: 60 })
   },
 
-  onClosePicker: function () {
+  onClosePicker() {
     this.setData({ showPicker: false })
   },
 
-  onSelectPreset: function (e) {
-    var val = e.currentTarget.dataset.value
+  onSelectPreset(e) {
+    const val = e.currentTarget.dataset.value
     this.setData({ customDuration: val, customInput: '' })
   },
 
-  onCustomInput: function (e) {
-    var val = parseInt(e.detail.value) || 0
+  onCustomInput(e) {
+    const val = parseInt(e.detail.value) || 0
     this.setData({ customInput: e.detail.value, customDuration: val })
   },
 
-  onConfirmFree: function () {
-    var dur = this.data.customDuration
+  onConfirmFree() {
+    const dur = this.data.customDuration
     if (!dur || dur <= 0) {
       wx.showToast({ title: '请输入有效时长', icon: 'none' })
       return
     }
     this.setData({ showPicker: false })
-    wx.navigateTo({ url: '/pages/timer/timer?free=' + dur })
+    wx.navigateTo({ url: `/pages/timer/timer?free=${dur}` })
   },
 
-  noop: function () {}
+  noop() {}
 })
diff --git a/pages/records/records.js b/pages/records/records.js
index e7a104e..36a2a8c 100644
--- a/pages/records/records.js
+++ b/pages/records/records.js
@@ -1,6 +1,6 @@
-var storage = require('../../utils/storage')
-var util = require('../../utils/util')
-var themeMod = require('../../utils/theme')
+const storage = require('../../utils/storage')
+const util = require('../../utils/util')
+const themeMod = require('../../utils/theme')
 
 Page({
   data: {
@@ -19,36 +19,31 @@ Page({
     dayDetail: {}
   },
 
-  onLoad: function () {
+  onLoad() {
     this.refresh()
   },
 
-  onShow: function () {
+  onShow() {
     themeMod.applyThemeToPage(this)
     try {
-      var tb = this.getTabBar()
+      const tb = this.getTabBar()
       if (tb) tb.setData({ selected: 1 })
     } catch (e) {}
     this.refresh()
   },
 
-  onPullDownRefresh: function () {
+  onPullDownRefresh() {
     this.refresh()
     wx.stopPullDownRefresh()
   },
 
-  refresh: function () {
-    var stats = storage.getTotalStats()
-    var monthKey = this.data.currentYear + '-' +
-      (this.data.currentMonth < 10 ? '0' : '') + this.data.currentMonth
-    var records = storage.getRecordsByMonth(monthKey)
+  refresh() {
+    const stats = storage.getTotalStats()
+    const monthKey = `${this.data.currentYear}-${String(this.data.currentMonth).padStart(2, '0')}`
+    const records = storage.getRecordsByMonth(monthKey)
 
-    var allRecords = []
-    var all = storage.getRecords()
-    Object.keys(all).forEach(function (key) {
-      allRecords = allRecords.concat(all[key])
-    })
-    allRecords.sort(function (a, b) { return b.date.localeCompare(a.date) })
+    const allRecords = Object.values(storage.getRecords()).flat()
+    allRecords.sort((a, b) => b.date.localeCompare(a.date))
 
     this.setData({
       totalDuration: stats.totalDuration,
@@ -61,48 +56,38 @@ Page({
     })
   },
 
-  onPrevMonth: function () {
-    var year = this.data.currentYear
-    var month = this.data.currentMonth
-    if (month === 1) {
-      year--
-      month = 12
+  onPrevMonth() {
+    let { currentYear, currentMonth } = this.data
+    if (currentMonth === 1) {
+      currentYear--
+      currentMonth = 12
     } else {
-      month--
+      currentMonth--
     }
-    this.setData({ currentYear: year, currentMonth: month })
+    this.setData({ currentYear, currentMonth })
     this.refresh()
   },
 
-  onNextMonth: function () {
-    var year = this.data.currentYear
-    var month = this.data.currentMonth
-    if (month === 12) {
-      year++
-      month = 1
+  onNextMonth() {
+    let { currentYear, currentMonth } = this.data
+    if (currentMonth === 12) {
+      currentYear++
+      currentMonth = 1
     } else {
-      month++
+      currentMonth++
     }
-    this.setData({ currentYear: year, currentMonth: month })
+    this.setData({ currentYear, currentMonth })
     this.refresh()
   },
 
-  onDayTap: function (e) {
-    var detail = e.detail
-    var dateStr = detail.year + '-' +
-      (detail.month < 10 ? '0' : '') + detail.month + '-' +
-      (detail.day < 10 ? '0' : '') + detail.day
+  onDayTap(e) {
+    const { year, month, day } = e.detail
+    const dateStr = `${year}-${String(month).padStart(2, '0')}-${String(day).padStart(2, '0')}`
 
-    var allRecords = []
-    var all = storage.getRecords()
-    Object.keys(all).forEach(function (key) {
-      allRecords = allRecords.concat(all[key])
-    })
-
-    var sessions = allRecords.filter(function (r) { return r.date === dateStr })
-    var totalDur = 0
-    sessions.forEach(function (r) { totalDur += r.duration })
-    var calories = Math.round(totalDur * 0.068)
+    const allRecords = Object.values(storage.getRecords()).flat()
+    const sessions = allRecords.filter(r => r.date === dateStr)
+    const totalDur = sessions.reduce((sum, r) => sum + r.duration, 0)
+    const calories = Math.round(totalDur * 0.068)
 
     this.setData({
       showDayDetail: true,
@@ -111,27 +96,26 @@ Page({
         sessions: sessions.length,
         duration: totalDur,
         durationText: util.formatDuration(totalDur),
-        calories: calories
+        calories
       }
     })
   },
 
-  onCloseDayDetail: function () {
+  onCloseDayDetail() {
     this.setData({ showDayDetail: false })
   },
 
-  noop: function () {},
+  noop() {},
 
-  onDeleteRecord: function (e) {
-    var id = e.currentTarget.dataset.id
-    var self = this
+  onDeleteRecord(e) {
+    const id = e.currentTarget.dataset.id
     wx.showModal({
       title: '删除记录',
       content: '确定要删除这条训练记录吗？',
-      success: function (res) {
+      success: (res) => {
         if (res.confirm) {
           storage.deleteRecord(id)
-          self.refresh()
+          this.refresh()
           wx.showToast({ title: '已删除', icon: 'none', duration: 1200 })
         }
       }
diff --git a/pages/settings/settings.js b/pages/settings/settings.js
index 8b9f348..df1866b 100644
--- a/pages/settings/settings.js
+++ b/pages/settings/settings.js
@@ -1,5 +1,5 @@
-var storage = require('../../utils/storage')
-var themeMod = require('../../utils/theme')
+const storage = require('../../utils/storage')
+const themeMod = require('../../utils/theme')
 
 Page({
   data: {
@@ -19,9 +19,9 @@ Page({
     vibrate: true
   },
 
-  onLoad: function () {
-    var s = storage.getSettings()
-    var theme = themeMod.getCurrentTheme()
+  onLoad() {
+    const s = storage.getSettings()
+    const theme = themeMod.getCurrentTheme()
     themeMod.applyThemeToPage(this)
     this.setData({
       currentPlanId: s.planId,
@@ -33,70 +33,68 @@ Page({
     })
   },
 
-  onShow: function () {
+  onShow() {
     try {
-      var tb = this.getTabBar()
+      const tb = this.getTabBar()
       if (tb) tb.setData({ selected: 2 })
     } catch (e) {}
     themeMod.applyThemeToPage(this)
   },
 
-  onSelectTheme: function (e) {
-    var id = e.currentTarget.dataset.id
-    var theme = themeMod.setTheme(id)
+  onSelectTheme(e) {
+    const id = e.currentTarget.dataset.id
+    const theme = themeMod.setTheme(id)
     this.setData({ currentThemeId: id })
 
     try {
-      var tb = this.getTabBar()
-      if (tb) {
-        tb.setData({ themeStyle: themeMod.getThemeStyle(theme) })
-      }
+      const tb = this.getTabBar()
+      if (tb) tb.setData({ themeStyle: themeMod.getThemeStyle(theme) })
     } catch (e) {}
 
     themeMod.applyThemeToPage(this)
   },
 
-  onSelectPlan: function (e) {
-    var planId = e.currentTarget.dataset.id
-    var s = storage.getSettings()
+  onSelectPlan(e) {
+    const planId = e.currentTarget.dataset.id
+    const s = storage.getSettings()
     s.planId = planId
     storage.saveSettings(s)
     this.setData({ currentPlanId: planId })
     wx.showToast({ title: '计划已切换', icon: 'success', duration: 1200 })
   },
 
-  onToggleReminder: function (e) {
-    var s = storage.getSettings()
+  onToggleReminder(e) {
+    const s = storage.getSettings()
     s.dailyReminder = e.detail.value
     storage.saveSettings(s)
     this.setData({ dailyReminder: e.detail.value })
   },
 
-  onReminderTimeChange: function (e) {
-    var s = storage.getSettings()
+  onReminderTimeChange(e) {
+    const s = storage.getSettings()
     s.reminderTime = e.detail.value
     storage.saveSettings(s)
     this.setData({ reminderTime: e.detail.value })
   },
 
-  onToggleVoice: function (e) {
-    var s = storage.getSettings()
+  onToggleVoice(e) {
+    const s = storage.getSettings()
     s.voiceGuide = e.detail.value
     storage.saveSettings(s)
     this.setData({ voiceGuide: e.detail.value })
   },
 
-  onToggleVibrate: function (e) {
-    var s = storage.getSettings()
+  onToggleVibrate(e) {
+    const s = storage.getSettings()
     s.vibrate = e.detail.value
     storage.saveSettings(s)
     this.setData({ vibrate: e.detail.value })
   },
 
-  onCopyWechat: function () {
+  onCopyWechat() {
     wx.setClipboardData({
       data: '刘承',
-      success: function () {
+      success: () => {
         wx.showToast({ title: '已复制', icon: 'success', duration: 1500 })
       }
     })
diff --git a/pages/timer/timer.js b/pages/timer/timer.js
index 704b693..b5e9d30 100644
--- a/pages/timer/timer.js
+++ b/pages/timer/timer.js
@@ -1,7 +1,7 @@
-var Timer = require('../../utils/timer')
-var storage = require('../../utils/storage')
-var planMod = require('../../utils/plan')
-var themeMod = require('../../utils/theme')
+const Timer = require('../../utils/timer')
+const storage = require('../../utils/storage')
+const planMod = require('../../utils/plan')
+const themeMod = require('../../utils/theme')
 
 Page({
   data: {
@@ -19,26 +19,21 @@ Page({
     isFreeMode: false
   },
 
-  onLoad: function (options) {
+  onLoad(options) {
     themeMod.applyThemeToPage(this)
 
-    var target
-    var planDay = 1
-    var isFreeMode = false
+    let target
+    let planDay = 1
+    let isFreeMode = false
 
     if (options && options.free) {
       target = parseInt(options.free) || 60
       isFreeMode = true
     } else {
-      var settings = storage.getSettings()
-      var records = []
-      var allRecords = storage.getRecords()
-      Object.keys(allRecords).forEach(function (key) {
-        records = records.concat(allRecords[key])
-      })
-
-      var plan = planMod.getPlan(settings.planId)
-      planDay = planMod.getPlanDay(settings.planId, records)
+      const settings = storage.getSettings()
+      const allRecords = Object.values(storage.getRecords()).flat()
+      const plan = planMod.getPlan(settings.planId)
+      planDay = planMod.getPlanDay(settings.planId, allRecords)
       target = planMod.getTodayTarget(settings.planId, Math.min(planDay, plan.totalDays))
     }
 
@@ -47,19 +42,18 @@ Page({
       remaining: target,
       todayTarget: target,
       planDay: isFreeMode ? 0 : Math.min(planDay, 99),
-      isFreeMode: isFreeMode
+      isFreeMode
     })
 
-    var self = this
     this._timer = new Timer({
-      onTick: function (tick) {
-        self.setData({
+      onTick: (tick) => {
+        this.setData({
           remaining: tick.remaining > 0 ? tick.remaining : 0,
-          overtime: tick.remaining <= 0 ? tick.elapsed - self.data.duration : 0
+          overtime: tick.remaining <= 0 ? tick.elapsed - this.data.duration : 0
         })
       },
-      onComplete: function () {
-        self.setData({ status: 'completed', isCompleted: true })
+      onComplete: () => {
+        this.setData({ status: 'completed', isCompleted: true })
         if (storage.getSettings().vibrate) {
           try { wx.vibrateLong() } catch (e) {}
         }
@@ -68,11 +62,11 @@ Page({
     })
   },
 
-  onUnload: function () {
+  onUnload() {
     if (this._timer) this._timer.stop()
   },
 
-  onStart: function () {
+  onStart() {
     if (this.data.isPaused) {
       this._timer.resume()
       this.setData({ isRunning: true, isPaused: false, status: 'running' })
@@ -83,26 +77,25 @@ Page({
     this.setData({ isRunning: true, status: 'running' })
   },
 
-  onPause: function () {
+  onPause() {
     if (!this.data.isRunning || this.data.isPaused) return
     this._timer.pause()
     this.setData({ isPaused: true, status: 'paused' })
   },
 
-  onStop: function () {
-    var self = this
+  onStop() {
     wx.showModal({
       title: '结束训练',
       content: '确定要结束本次训练吗?',
-      success: function (res) {
-        if (res.confirm) self.finishTraining()
+      success: (res) => {
+        if (res.confirm) this.finishTraining()
       }
     })
   },
 
-  finishTraining: function () {
-    var elapsed = this._timer.stop()
-    var today = storage.getToday()
+  finishTraining() {
+    const elapsed = this._timer.stop()
+    const today = storage.getToday()
     storage.saveRecord({
       date: today,
       duration: elapsed,
@@ -111,7 +104,7 @@ Page({
     })
     storage.updateStreak(today)
 
-    wx.showToast({ title: '已记录 ' + elapsed + '秒', icon: 'none', duration: 1500 })
-    setTimeout(function () { wx.navigateBack() }, 1500)
+    wx.showToast({ title: `已记录 ${elapsed}秒`, icon: 'none', duration: 1500 })
+    setTimeout(() => { wx.navigateBack() }, 1500)
   }
 })
diff --git a/utils/plan.js b/utils/plan.js
index 271edd9..bf0e580 100644
--- a/utils/plan.js
+++ b/utils/plan.js
@@ -1,73 +1,52 @@
-var plans = {
+const { formatDate } = require('./util')
+
+const plans = {
   beginner: {
     id: 'beginner',
     name: '初级 (7天)',
     totalDays: 7,
     description: '适合初学者，从30秒起步',
-    days: [
-      { day: 1, target: 30 },
-      { day: 2, target: 40 },
-      { day: 3, target: 50 },
-      { day: 4, target: 60 },
-      { day: 5, target: 70 },
-      { day: 6, target: 80 },
-      { day: 7, target: 90 }
-    ]
+    days: Array.from({ length: 7 }, (_, i) => ({ day: i + 1, target: 30 + i * 10 }))
   },
   intermediate: {
     id: 'intermediate',
     name: '中级 (14天)',
     totalDays: 14,
     description: '有一定基础，从60秒起步',
-    days: [
-      { day: 1, target: 60 }, { day: 2, target: 60 },
-      { day: 3, target: 75 }, { day: 4, target: 75 },
-      { day: 5, target: 90 }, { day: 6, target: 90 },
-      { day: 7, target: 105 }, { day: 8, target: 105 },
-      { day: 9, target: 120 }, { day: 10, target: 120 },
-      { day: 11, target: 135 }, { day: 12, target: 135 },
-      { day: 13, target: 150 }, { day: 14, target: 150 }
-    ]
+    days: Array.from({ length: 14 }, (_, i) => {
+      const pair = Math.floor(i / 2)
+      return { day: i + 1, target: 60 + pair * 15 }
+    })
   },
   advanced: {
     id: 'advanced',
     name: '高级 (30天)',
     totalDays: 30,
     description: '挑战自我，从90秒起步',
-    days: (function () {
-      var arr = []
-      for (var i = 1; i <= 30; i++) {
-        arr.push({ day: i, target: 90 + Math.floor((i - 1) / 3) * 15 })
-      }
-      return arr
-    })()
+    days: Array.from({ length: 30 }, (_, i) => ({
+      day: i + 1,
+      target: 90 + Math.floor(i / 3) * 15
+    }))
   }
 }
 
-function getPlan(planId) {
-  return plans[planId] || plans.beginner
+const getPlan = (planId) => plans[planId] || plans.beginner
+
+const getTodayTarget = (planId, currentDay) => {
+  const plan = getPlan(planId)
+  const day = plan.days.find(d => d.day === currentDay)
+  return day ? day.target : plan.days[0].target
 }
 
-function getTodayTarget(planId, currentDay) {
-  var plan = getPlan(planId)
-  for (var i = 0; i < plan.days.length; i++) {
-    if (plan.days[i].day === currentDay) return plan.days[i].target
-  }
-  return plan.days[0].target
-}
-
-function getPlanDay(planId, records) {
-  var plan = getPlan(planId)
-  var now = new Date()
-  var today = now.getFullYear() + '-' +
-    ('0' + (now.getMonth() + 1)).slice(-2) + '-' +
-    ('0' + now.getDate()).slice(-2)
-  var dates = {}
-  records.forEach(function (r) {
-    if (r.date !== today) dates[r.date] = true
-  })
-  var trainedDays = Object.keys(dates).length
+const getPlanDay = (planId, records) => {
+  const plan = getPlan(planId)
+  const today = formatDate(new Date())
+  const trainedDays = new Set(
+    records
+      .filter(r => r.date !== today && r.planId === planId)
+      .map(r => r.date)
+  ).size
   return Math.min(trainedDays + 1, plan.totalDays)
 }
 
-module.exports = { plans: plans, getPlan: getPlan, getTodayTarget: getTodayTarget, getPlanDay: getPlanDay }
+module.exports = { plans, getPlan, getTodayTarget, getPlanDay }
diff --git a/utils/storage.js b/utils/storage.js
index 1665e9c..b69f611 100644
--- a/utils/storage.js
+++ b/utils/storage.js
@@ -1,73 +1,68 @@
-var RECORDS_KEY = 'training_records'
-var SETTINGS_KEY = 'user_settings'
-var STREAK_KEY = 'current_streak'
+const { formatDate } = require('./util')
 
-function getRecords() {
-  return wx.getStorageSync(RECORDS_KEY) || {}
-}
+const RECORDS_KEY = 'training_records'
+const SETTINGS_KEY = 'user_settings'
+const STREAK_KEY = 'current_streak'
 
-function saveRecord(record) {
+const getRecords = () => wx.getStorageSync(RECORDS_KEY) || {}
+
+const saveRecord = (record) => {
   record.id = Date.now()
-  var records = getRecords()
-  var month = record.date.substring(0, 7)
+  const records = getRecords()
+  const month = record.date.substring(0, 7)
   if (!records[month]) records[month] = []
   records[month].push(record)
-  records[month].sort(function (a, b) { return b.date.localeCompare(a.date) })
+  records[month].sort((a, b) => b.date.localeCompare(a.date))
   wx.setStorageSync(RECORDS_KEY, records)
 }
 
-function deleteRecord(recordId) {
-  var records = getRecords()
-  Object.keys(records).forEach(function (month) {
-    records[month] = records[month].filter(function (r) { return r.id !== recordId })
+const deleteRecord = (recordId) => {
+  const records = getRecords()
+  Object.keys(records).forEach((month) => {
+    records[month] = records[month].filter((r) => r.id !== recordId)
     if (records[month].length === 0) delete records[month]
   })
   wx.setStorageSync(RECORDS_KEY, records)
 }
 
-function getRecordsByMonth(month) {
-  var records = getRecords()
+const getRecordsByMonth = (month) => {
+  const records = getRecords()
   return records[month] || []
 }
 
-function getTotalStats() {
-  var records = getRecords()
-  var totalDuration = 0
-  var totalSessions = 0
-  var maxDuration = 0
-  Object.keys(records).forEach(function (key) {
-    var list = records[key]
-    list.forEach(function (r) {
+const getTotalStats = () => {
+  const records = getRecords()
+  let totalDuration = 0
+  let totalSessions = 0
+  let maxDuration = 0
+  Object.keys(records).forEach((key) => {
+    records[key].forEach((r) => {
       totalDuration += r.duration
       totalSessions++
       if (r.duration > maxDuration) maxDuration = r.duration
     })
   })
-  return { totalDuration: totalDuration, totalSessions: totalSessions, maxDuration: maxDuration }
+  return { totalDuration, totalSessions, maxDuration }
 }
 
-function getSettings() {
-  return wx.getStorageSync(SETTINGS_KEY) || {
-    planId: 'beginner',
-    dailyReminder: true,
-    reminderTime: '08:00',
-    voiceGuide: true,
-    vibrate: true
-  }
+const getSettings = () => wx.getStorageSync(SETTINGS_KEY) || {
+  planId: 'beginner',
+  dailyReminder: true,
+  reminderTime: '08:00',
+  voiceGuide: true,
+  vibrate: true
 }
 
-function saveSettings(settings) {
+const saveSettings = (settings) => {
   wx.setStorageSync(SETTINGS_KEY, settings)
 }
 
-function getStreak() {
-  return wx.getStorageSync(STREAK_KEY) || { count: 0, lastDate: '' }
-}
+const getStreak = () => wx.getStorageSync(STREAK_KEY) || { count: 0, lastDate: '' }
 
-function updateStreak(date) {
-  var streak = getStreak()
-  var today = date || getToday()
-  var yesterday = getDateOffset(today, -1)
+const updateStreak = (date) => {
+  const streak = getStreak()
+  const today = date || getToday()
+  const yesterday = getDateOffset(today, -1)
 
   if (streak.lastDate === today) return streak
 
@@ -81,52 +76,42 @@ function updateStreak(date) {
   return streak
 }
 
-function getToday() {
-  return formatDate(new Date())
-}
+const getToday = () => formatDate(new Date())
 
-function formatDate(date) {
-  var y = date.getFullYear()
-  var m = String(date.getMonth() + 1)
-  if (m.length < 2) m = '0' + m
-  var d = String(date.getDate())
-  if (d.length < 2) d = '0' + d
-  return y + '-' + m + '-' + d
-}
-
-function getDateOffset(dateStr, offset) {
-  var d = new Date(dateStr)
+const getDateOffset = (dateStr, offset) => {
+  const d = new Date(dateStr)
   d.setDate(d.getDate() + offset)
   return formatDate(d)
 }
 
-function getTodayRecord() {
-  var today = getToday()
-  var month = today.substring(0, 7)
-  var records = getRecordsByMonth(month)
-  var totalDuration = 0
-  var hasRecord = false
-  for (var i = 0; i < records.length; i++) {
-    if (records[i].date === today) {
-      totalDuration += records[i].duration
-      hasRecord = true
-    }
-  }
+const getTodayRecord = () => {
+  const today = getToday()
+  const records = getRecords()
+  let totalDuration = 0
+  let hasRecord = false
+  Object.keys(records).forEach((month) => {
+    records[month].forEach((r) => {
+      if (r.date === today) {
+        totalDuration += r.duration
+        hasRecord = true
+      }
+    })
+  })
   return hasRecord ? { date: today, duration: totalDuration } : null
 }
 
 module.exports = {
-  getRecords: getRecords,
-  saveRecord: saveRecord,
-  deleteRecord: deleteRecord,
-  getRecordsByMonth: getRecordsByMonth,
-  getTotalStats: getTotalStats,
-  getSettings: getSettings,
-  saveSettings: saveSettings,
-  getStreak: getStreak,
-  updateStreak: updateStreak,
-  getToday: getToday,
-  formatDate: formatDate,
-  getDateOffset: getDateOffset,
-  getTodayRecord: getTodayRecord
+  getRecords,
+  saveRecord,
+  deleteRecord,
+  getRecordsByMonth,
+  getTotalStats,
+  getSettings,
+  saveSettings,
+  getStreak,
+  updateStreak,
+  getToday,
+  formatDate,
+  getDateOffset,
+  getTodayRecord
 }
diff --git a/utils/theme.js b/utils/theme.js
index 1182a23..485bc13 100644
--- a/utils/theme.js
+++ b/utils/theme.js
@@ -1,4 +1,4 @@
-var THEMES = [
+const THEMES = [
   {
     id: 'orange',
     name: '活力橙',
@@ -41,25 +41,23 @@ var THEMES = [
   }
 ]
 
-var DEFAULT_THEME_ID = 'orange'
-var THEME_KEY = 'app_theme'
-var _lastNavColor = ''
-var _navColorTimer = null
+const DEFAULT_THEME_ID = 'orange'
+const THEME_KEY = 'app_theme'
+let _lastNavColor = ''
+let _navColorTimer = null
 
-function getThemeById(id) {
-  return THEMES.find(function (t) { return t.id === id }) || THEMES[0]
-}
+const getThemeById = (id) => THEMES.find(t => t.id === id) || THEMES[0]
 
-function getCurrentTheme() {
-  var id = wx.getStorageSync(THEME_KEY) || DEFAULT_THEME_ID
+const getCurrentTheme = () => {
+  const id = wx.getStorageSync(THEME_KEY) || DEFAULT_THEME_ID
   return getThemeById(id)
 }
 
-function _setNavBarColor(primary) {
+const _setNavBarColor = (primary) => {
   if (_lastNavColor === primary) return
   _lastNavColor = primary
   if (_navColorTimer) clearTimeout(_navColorTimer)
-  _navColorTimer = setTimeout(function () {
+  _navColorTimer = setTimeout(() => {
     try {
       wx.setNavigationBarColor({
         frontColor: '#ffffff',
@@ -69,35 +67,35 @@ function _setNavBarColor(primary) {
   }, 50)
 }
 
-function setTheme(id) {
+const setTheme = (id) => {
   wx.setStorageSync(THEME_KEY, id)
-  var theme = getThemeById(id)
+  const theme = getThemeById(id)
   _setNavBarColor(theme.primary)
-  var app = getApp()
+  const app = getApp()
   if (app && app.globalData) app.globalData.theme = theme
   return theme
 }
 
-function applyThemeToPage(self) {
-  var theme = getCurrentTheme()
+const applyThemeToPage = (self) => {
+  const theme = getCurrentTheme()
   self.setData({
-    theme: theme,
-    themeStyle: '--primary:' + theme.primary + ';--primary-light:' + theme.primaryLight + ';--primary-bg:' + theme.primaryBg + ';--primary-rgb:' + theme.primaryRgb + ';'
+    theme,
+    themeStyle: `--primary:${theme.primary};--primary-light:${theme.primaryLight};--primary-bg:${theme.primaryBg};--primary-rgb:${theme.primaryRgb};`
   })
   _setNavBarColor(theme.primary)
 }
 
-function getThemeStyle(theme) {
-  var t = theme || getCurrentTheme()
-  return '--primary:' + t.primary + ';--primary-light:' + t.primaryLight + ';--primary-bg:' + t.primaryBg + ';--primary-rgb:' + t.primaryRgb + ';'
+const getThemeStyle = (theme) => {
+  const t = theme || getCurrentTheme()
+  return `--primary:${t.primary};--primary-light:${t.primaryLight};--primary-bg:${t.primaryBg};--primary-rgb:${t.primaryRgb};`
 }
 
 module.exports = {
-  THEMES: THEMES,
-  DEFAULT_THEME_ID: DEFAULT_THEME_ID,
-  getThemeById: getThemeById,
-  getCurrentTheme: getCurrentTheme,
-  setTheme: setTheme,
-  applyThemeToPage: applyThemeToPage,
-  getThemeStyle: getThemeStyle
+  THEMES,
+  DEFAULT_THEME_ID,
+  getThemeById,
+  getCurrentTheme,
+  setTheme,
+  applyThemeToPage,
+  getThemeStyle
 }
diff --git a/utils/timer.js b/utils/timer.js
index f69cb0e..c0d1c41 100644
--- a/utils/timer.js
+++ b/utils/timer.js
@@ -1,92 +1,77 @@
-function Timer(options) {
-  options = options || {}
-  this.onTick = options.onTick || function () {}
-  this.onComplete = options.onComplete || function () {}
+class Timer {
+  constructor(options = {}) {
+    this.onTick = options.onTick || (() => {})
+    this.onComplete = options.onComplete || (() => {})
 
-  this._duration = 0
-  this._remaining = 0
-  this._elapsed = 0
-  this._startTime = 0
-  this._pausedTime = 0
-  this._intervalId = null
-  this._running = false
-  this._paused = false
-  this._completed = false
-}
-
-Timer.prototype.start = function (duration) {
-  this._duration = duration
-  this._remaining = duration
-  this._elapsed = 0
-  this._completed = false
-  this._running = true
-  this._paused = false
-  this._startTime = Date.now()
-  this._tick()
-  var self = this
-  this._intervalId = setInterval(function () { self._tick() }, 1000)
-}
-
-Timer.prototype.pause = function () {
-  if (!this._running || this._paused) return
-  this._paused = true
-  this._pausedTime = Date.now()
-  clearInterval(this._intervalId)
-  this._intervalId = null
-}
-
-Timer.prototype.resume = function () {
-  if (!this._running || !this._paused) return
-  this._startTime += Date.now() - this._pausedTime
-  this._paused = false
-  this._tick()
-  var self = this
-  this._intervalId = setInterval(function () { self._tick() }, 1000)
-}
-
-Timer.prototype.stop = function () {
-  this._running = false
-  this._paused = false
-  clearInterval(this._intervalId)
-  this._intervalId = null
-  return this._elapsed
-}
-
-Timer.prototype._tick = function () {
-  if (!this._running || this._paused) return
-  this._elapsed = Math.floor((Date.now() - this._startTime) / 1000)
-  this._remaining = Math.max(0, this._duration - this._elapsed)
-
-  this.onTick({
-    remaining: this._remaining,
-    elapsed: this._elapsed,
-    duration: this._duration
-  })
-
-  if (this._remaining <= 0 && !this._completed) {
-    this._completed = true
-    this.onComplete({ elapsed: this._elapsed, duration: this._duration })
+    this._duration = 0
+    this._remaining = 0
+    this._elapsed = 0
+    this._startTime = 0
+    this._pausedTime = 0
+    this._intervalId = null
+    this._running = false
+    this._paused = false
+    this._completed = false
   }
+
+  start(duration) {
+    this._duration = duration
+    this._remaining = duration
+    this._elapsed = 0
+    this._completed = false
+    this._running = true
+    this._paused = false
+    this._startTime = Date.now()
+    this._tick()
+    this._intervalId = setInterval(() => { this._tick() }, 1000)
+  }
+
+  pause() {
+    if (!this._running || this._paused) return
+    this._paused = true
+    this._pausedTime = Date.now()
+    clearInterval(this._intervalId)
+    this._intervalId = null
+  }
+
+  resume() {
+    if (!this._running || !this._paused) return
+    this._startTime += Date.now() - this._pausedTime
+    this._paused = false
+    this._tick()
+    this._intervalId = setInterval(() => { this._tick() }, 1000)
+  }
+
+  stop() {
+    this._running = false
+    this._paused = false
+    clearInterval(this._intervalId)
+    this._intervalId = null
+    return this._elapsed
+  }
+
+  _tick() {
+    if (!this._running || this._paused) return
+    this._elapsed = Math.floor((Date.now() - this._startTime) / 1000)
+    this._remaining = Math.max(0, this._duration - this._elapsed)
+
+    this.onTick({
+      remaining: this._remaining,
+      elapsed: this._elapsed,
+      duration: this._duration
+    })
+
+    if (this._remaining <= 0 && !this._completed) {
+      this._completed = true
+      this.onComplete({ elapsed: this._elapsed, duration: this._duration })
+    }
+  }
+
+  get isRunning() { return this._running && !this._paused }
+  get isPaused() { return this._paused }
+  get isCompleted() { return this._completed }
+  get remaining() { return this._remaining }
+  get elapsed() { return this._elapsed }
 }
 
-Object.defineProperty(Timer.prototype, 'isRunning', {
-  get: function () { return this._running && !this._paused }
-})
-
-Object.defineProperty(Timer.prototype, 'isPaused', {
-  get: function () { return this._paused }
-})
-
-Object.defineProperty(Timer.prototype, 'isCompleted', {
-  get: function () { return this._completed }
-})
-
-Object.defineProperty(Timer.prototype, 'remaining', {
-  get: function () { return this._remaining }
-})
-
-Object.defineProperty(Timer.prototype, 'elapsed', {
-  get: function () { return this._elapsed }
-})
-
 module.exports = Timer
diff --git a/utils/util.js b/utils/util.js
index d0ec503..dd4efab 100644
--- a/utils/util.js
+++ b/utils/util.js
@@ -1,31 +1,28 @@
-function formatTime(seconds) {
-  var m = Math.floor(seconds / 60)
-  var s = seconds % 60
-  return (m < 10 ? '0' : '') + m + ':' + (s < 10 ? '0' : '') + s
+const formatTime = (seconds) => {
+  const m = Math.floor(seconds / 60)
+  const s = seconds % 60
+  return `${String(m).padStart(2, '0')}:${String(s).padStart(2, '0')}`
 }
 
-function formatDuration(seconds) {
-  if (seconds < 60) return seconds + '秒'
-  var m = Math.floor(seconds / 60)
-  var s = seconds % 60
-  return s > 0 ? m + '分' + s + '秒' : m + '分钟'
+const formatDuration = (seconds) => {
+  if (seconds < 60) return `${seconds}秒`
+  const m = Math.floor(seconds / 60)
+  const s = seconds % 60
+  return s > 0 ? `${m}分${s}秒` : `${m}分钟`
 }
 
-function getDaysInMonth(year, month) {
-  return new Date(year, month, 0).getDate()
-}
+const getDaysInMonth = (year, month) => new Date(year, month, 0).getDate()
 
-function getMonthCalendar(year, month) {
-  var firstDay = new Date(year, month - 1, 1)
-  var lastDay = new Date(year, month, 0)
-  var daysInMonth = lastDay.getDate()
-  var startDayOfWeek = firstDay.getDay()
+const getMonthCalendar = (year, month) => {
+  const firstDay = new Date(year, month - 1, 1)
+  const daysInMonth = new Date(year, month, 0).getDate()
+  const startDayOfWeek = firstDay.getDay()
 
-  var weeks = []
-  var week = [null, null, null, null, null, null, null]
+  const weeks = []
+  let week = [null, null, null, null, null, null, null]
 
-  for (var d = 1; d <= daysInMonth; d++) {
-    var dow = (startDayOfWeek + d - 1) % 7
+  for (let d = 1; d <= daysInMonth; d++) {
+    const dow = (startDayOfWeek + d - 1) % 7
     week[dow] = d
     if (dow === 6 || d === daysInMonth) {
       weeks.push(week.slice())
@@ -36,9 +33,17 @@ function getMonthCalendar(year, month) {
   return weeks
 }
 
-module.exports = {
-  formatTime: formatTime,
-  formatDuration: formatDuration,
-  getDaysInMonth: getDaysInMonth,
-  getMonthCalendar: getMonthCalendar
+const formatDate = (date) => {
+  const y = date.getFullYear()
+  const m = String(date.getMonth() + 1).padStart(2, '0')
+  const d = String(date.getDate()).padStart(2, '0')
+  return `${y}-${m}-${d}`
+}
+
+module.exports = {
+  formatTime,
+  formatDuration,
+  getDaysInMonth,
+  getMonthCalendar,
+  formatDate
 }