When I was making a mini program, I sold a limited-time product and used a countdown. Because of this reason, when using the mini program on an Android phone, after putting the mini program in the background to run for a period of time, after entering the mini program again When the page goes blank or the click event fails, record it here

1. Related code files

I use a custom component to render here The

• External reference to the wxml file of the custom component

/* limitCommodity是一个数组，返回的是商品对象，包含商品价格、商品结束时间、商品图片等 */   

• The js file of the custom component

Component({ properties: { goods: Object }, data: { }, timer: null, /* 在组件实例进入页面节点树时执行，开始定时器 */ attached: function() { if(this.timer) { clearInterval(this.timer); } this.filterTime(); let that = this; this.timer = setInterval(function () { that.filterTime(); }, 1000) }, /* 在组件实例被从页面节点树移除时执行，将定时器清除 */ detached: function() { clearInterval(this.timer); this.timer = null; }, methods: { /* 用于将时间戳转换成自定义的时间格式 */ filterTime() { let totalTime = new Date(parseInt(this.data.goods.endtime) * 1000) - new Date(); let days = parseInt(totalTime / 1000 / 60 / 60 / 24, 10); let hours = parseInt(totalTime / 1000 / 60 / 60 % 24, 10); let minutes = parseInt(totalTime / 1000 / 60 % 60, 10); let seconds = parseInt(totalTime / 1000 % 60, 10); let day = days >= 10 ? days : '0' + days; day = day == 0 ? '' : day + '天'; let hour = hours >= 10 ? hours : '0' + hours; let minute = minutes >= 10 ? minutes : '0' + minutes; let second = seconds >= 10 ? seconds : '0' + seconds; this.setData({ limitTime: day + hour + ":" + minute + ":" + second }) }, } })

2. Cause

• Because when custom components are introduced externally, the timer is directly called And the setData operation is performed, which results in that when this component is referenced externally, if the length of the incoming product array is large, the timer increases and the setData operation also continues to increase
• More setData will lead to more memory usage

3. Improvement method

The improvement method is to reduce setData operations

• You can customize another component to pass the entire array into
• and then calculate the time in the product array
• Improved js file

Component({ properties: { limitCommodity:Array }, data: { }, timeOut:null, /* 在组件实例进入页面节点树时执行 */ attached(){ this.calculate(); }, /* 在组件实例被从页面节点树移除时执行，将定时器清除 */ detached(){ clearTimeout(this.timeOut); this.timeOut = null; }, methods: { filterTime(endtime) { let totalTime = new Date(parseInt(endtime) * 1000) - new Date(); let days = parseInt(totalTime / 1000 / 60 / 60 / 24, 10); let hours = parseInt(totalTime / 1000 / 60 / 60 % 24, 10); let minutes = parseInt(totalTime / 1000 / 60 % 60, 10); let seconds = parseInt(totalTime / 1000 % 60, 10); let day = days >= 10 ? days : '0' + days; day = day == 0 ? '' : day + '天'; let hour = hours >= 10 ? hours : '0' + hours; let minute = minutes >= 10 ? minutes : '0' + minutes; let second = seconds >= 10 ? seconds : '0' + seconds; return day + hour + ":" + minute + ":" + second }, calculate(){ let limitCommodity = this.data.limitCommodity; for (let i = 0; i < limitCommodity.length;i++){ limitCommodity[i]['endtime_date'] = this.filterTime(limitCommodity[i]['endtime']) } this.setData({ limitCommodity }) this.timeOut = setTimeout(()=>{ this.calculate(); },1000); } } })

• The improvement is to calculate the time and then return the time, and setData is the entire product list array, so Reduced the number of setData times

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