JS防抖和节流实例解析

function debounce(fn, wait) {
  var timeout = null;   //定义一个定时器
  return function() {
    if(timeout !== null) 
        clearTimeout(timeout); //清除这个定时器
    timeout = setTimeout(fn, wait); 
  }
}
// 处理函数
function handle() {
  console.log(Math.random()); 
}
// 滚动事件
window.addEventListener('scroll', debounce(handle, 1000));

var throttle = function(func, delay) {
  var prev = Date.now();
  return function() {
    var context = this;  //this指向window
    var args = arguments;
    var now = Date.now();
    if (now - prev >= delay) {
      func.apply(context, args);
      prev = Date.now();
    }
  }
}
function handle() {
  console.log(Math.random());
}
window.addEventListener('scroll', throttle(handle, 1000));

var throttle = function(func, delay) {
  var timer = null;
  return function() {
    var context = this;
    var args = arguments;
    if (!timer) {
      timer = setTimeout(function() {
        func.apply(context, args);
        timer = null;
      }, delay);
    }
  }
}
function handle() {
  console.log(Math.random());
}
window.addEventListener('scroll', throttle(handle, 1000));

var throttle = function(func, delay) {
   var timer = null;
   var startTime = Date.now(); //设置开始时间
   return function() {
       var curTime = Date.now();
       var remaining = delay - (curTime - startTime); //剩余时间
       var context = this;
       var args = arguments;
       clearTimeout(timer);
       if (remaining <= 0) {   // 第一次触发立即执行
          func.apply(context, args);
          startTime = Date.now();
       } else {
          timer = setTimeout(func, remaining);  //取消当前计数器并计算新的remaining
       }
   }
}
function handle() {
   console.log(Math.random());
}
 window.addEventListener('scroll', throttle(handle, 1000));