微信小程序电商常用倒计时
wxml文件放个text
<text>second: {{second}} micro second:{{micro_second}}</text>
在js文件中调用
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function countdown(that) { var second = that.data.second if (second == 0) { // console.log("Time Out..."); that.setData({ second: "Time Out..." }); return ; } var time = setTimeout(function(){ that.setData({ second: second - 1 }); countdown(that); } ,1000)}Page({ data: { second: 3 }, onLoad: function() { countdown(this); }}); |
运行验证下，从10走到1s，然后显示时间到。
于是继续将毫秒完善，注意毫秒的步长受限于系统的时间频率，于是我们精确到0.01s即10ms
js
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/* 秒级倒计时 */function countdown(that) { var second = that.data.second if (second == 0) { that.setData({ second: "Time out!", micro_second: "micro_second too." }); clearTimeout(micro_timer); return ; } var timer = setTimeout(function(){ that.setData({ second: second - 1 }); countdown(that); } ,1000)}/* 毫秒级倒计时 */// 初始毫秒数，同时用作归零var micro_second_init = 100;// 当前毫秒数var micro_second_current = micro_second_init;// 毫秒计时器var micro_timer;function countdown4micro(that) { if (micro_second_current <= 0) { micro_second_current = micro_second_init; } micro_timer = setTimeout(function(){ that.setData({ micro_second: micro_second_current - 1 }); micro_second_current--; countdown4micro(that); } ,10)}Page({ data: { second: 2, micro_second: micro_second_init }, onLoad: function() { countdown(this); countdown4micro(this); }}); |
wxml文件
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<text style="display: block;">second: {{second}}s</text><text>{{micro_second}}</text> |
如此，当秒级运行完毕时，毫秒级timer即clearTimeout，并将字本显示为'micro_second too'
再添加一个countdown4micro方法，使得显示剩余 0:3:19 89这样形式的倒数
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function dateformat(second) { var dateStr = ""; var hr = Math.floor(second / 3600); var min = Math.floor((second - hr * 3600) / 60); var sec = (second - hr * 3600 - min * 60);// equal to => var sec = second % 60; dateStr = hr + ":" + min + ":" + sec; return dateStr;}目前有2个时钟，影响性能，合并下去掉countdown，于是countdown4micro变成以下的样子：function countdown4micro(that) { var loop_second = Math.floor(loop_index / 100); // 得知经历了1s if (cost_micro_second != loop_second) { // 赋予新值 cost_micro_second = loop_second; // 总秒数减1 total_second--; } // 每隔一秒，显示值减1; 渲染倒计时时钟 that.setData({ clock:dateformat(total_second - 1) }); if (total_second == 0) { that.setData({ // micro_second: "", clock:"时间到" }); clearTimeout(micro_timer); return ; } if (micro_second_current <= 0) { micro_second_current = micro_second_init; } micro_timer = setTimeout(function(){ that.setData({ micro_second: micro_second_current - 1 }); micro_second_current--; // 放在最后++，不然时钟停止时还有10毫秒剩余 loop_index ++; countdown4micro(that); } ,10)} |
如此这般，毫秒与时分秒是分别运行渲染的，再次改造，程序可读性更好。dateformat针对于毫秒操作，而不接受秒为数。同时还省却了计算100次为1s的运算
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/** * 需要一个目标日期，初始化时，先得出到当前时间还有剩余多少秒 * 1.将秒数换成格式化输出为XX天XX小时XX分钟XX秒 XX * 2.提供一个时钟，每10ms运行一次，渲染时钟，再总ms数自减10 * 3.剩余的秒次为零时，return，给出tips提示说，已经截止 */// 定义一个总毫秒数，以一分钟为例。TODO，传入一个时间点，转换成总毫秒数var total_micro_second = 2 * 1000;/* 毫秒级倒计时 */function countdown(that) { // 渲染倒计时时钟 that.setData({ clock:dateformat(total_micro_second) }); if (total_micro_second <= 0) { that.setData({ clock:"已经截止" }); // timeout则跳出递归 return ; } setTimeout(function(){ // 放在最后-- total_micro_second -= 10; countdown(that); } ,10)}// 时间格式化输出，如3:25:19 86。每10ms都会调用一次function dateformat(micro_second) { // 秒数 var second = Math.floor(micro_second / 1000); // 小时位 var hr = Math.floor(second / 3600); // 分钟位 var min = Math.floor((second - hr * 3600) / 60); // 秒位 var sec = (second - hr * 3600 - min * 60);// equal to => var sec = second % 60; // 毫秒位，保留2位 var micro_sec = Math.floor((micro_second % 1000) / 10); return hr + ":" + min + ":" + sec + " " + micro_sec;}Page({ data: { clock: '' }, onLoad: function() { countdown(this); }}); |
经过如上优化，代码量减少一半，运行效率也高了。
