JavaScript防抖动与节流处理

// 将会包装事件的 debounce 函数
function debounce(fn, delay) {
  // 维护一个 timer
  let timer = null;
 
  return function() {
    // 通过 ‘this' 和 ‘arguments' 获取函数的作用域和变量
    let context = this;
    let args = arguments;
 
    clearTimeout(timer);
    timer = setTimeout(function() {
      fn.apply(context, args);
    }, delay);
  }
}

// 当用户滚动时被调用的函数
function foo() {
  console.log('You are scrolling!');
 
}
 
// 在 debounce 中包装我们的函数，过 2 秒触发一次
let elem = document.getElementById('container');
elem.addEventListener('scroll', debounce(foo, 2000));

function debouce(func,delay,immediate){
    var timer = null;
    return function(){
        var context = this;
        var args = arguments;
        if(timer) clearTimeout(time);
        if(immediate){
            //根据距离上次触发操作的时间是否到达delay来决定是否要现在执行函数
            var doNow = !timer;
            //每一次都重新设置timer，就是要保证每一次执行的至少delay秒后才可以执行
            timer = setTimeout(function(){
                timer = null;
            },delay);
            //立即执行
            if(doNow){
                func.apply(context,args);
            }
        }else{
            timer = setTimeout(function(){
                func.apply(context,args);
            },delay);
        }
    }
}

var throttle = function(func,delay){
    var prev = Date.now();
    return function(){
        var context = this;
        var args = arguments;
        var now = Date.now();
        if(now-prev>=delay){
            func.apply(context,args);
            prev = Date.now();
        }
    }
}

var throttle = fucntion(func,delay){
    var timer = null;
 
    return funtion(){
        var context = this;
        var args = arguments;
        if(!timer){
            timer = setTimeout(function(){
                func.apply(context,args);
                timer = null;
            },delay);
        }
    }
}

var throttle = function(func,delay){
    var timer = null;
    var startTime = Date.now();
 
    return function(){
        var curTime = Date.now();
        var remaining = delay-(curTime-startTime);
        var context = this;
        var args = arguments;
 
        clearTimeout(timer);
        if(remaining<=0){
            func.apply(context,args);
            startTime = Date.now();
        }else{
            timer = setTimeout(func,remaining);
        }
    }
}