js定时器优化

先看以下两看计时器

setInterval

function sleep(time) {
  let startTime = window.performance.now();
  while (window.performance.now() - startTime < time) {}
}

function test(){
    count++;
    console.log(`第${count}次开始 ${getTime.now() - startTime}`); 
    // 显示开始时间
    //sleep(100); // 程序滞留500ms
    console.log(`第${count}次结束 ${getTime.now() - startTime}`); // 显示结束时间
    count>1000 && clearInterval(t);
}

let count = 0;
let getTime = window.performance;
let startTime = getTime.now();

var t = setInterval(test , 500); // 300ms间隔

最后结果：

再来看下setTimeout

function sleep(time) {
  let startTime = window.performance.now();
  while (window.performance.now() - startTime < time) {}
}

function test(){
  console.log(`第${count}次开始 ${getTime.now() - startTime}`); // 显示开始时间
  //sleep(500); // 程序滞留500ms
  console.log(`第${count}次结束 ${getTime.now() - startTime}`); // 显示结束时间
  count += 1;
  if(count<1000){setTimeout(test,500);}
}

var startTime0 = new Date().getTime();
let count = 0;
let getTime = window.performance;
let startTime = getTime.now();
var t;
//setTimeout(test,500); // 300ms间隔

setTimeout(function () {
  console.log(`第${count}次开始 ${getTime.now() - startTime}`); // 显示开始时间
  //sleep(500); // 程序滞留500ms
  console.log(`第${count}次结束 ${getTime.now() - startTime}`); // 显示结束时间

  count += 1;
  var offset = new Date().getTime() - (startTime0 + count * 500);
    var nextTime = 500 - offset;
//console.log(nextTime);
    if (nextTime < 0) nextTime = 0;
  
  if(count<200){setTimeout(arguments.callee, nextTime);}
            
        }, 500)