防抖与节流

let num = 1;
let content = document.getElementById('content');
function count() {
  content.innerHTML = num++;
};
content.onmousemove = throttle2(count, 500);

//防抖非立即执行版本:
function debounce1(fun, wait) {
    let t;
    return function () {
    let context = this, args = arguments;
        t ? clearTimeout(t) : undefined;
        t = setTimeout(() => {
            fun.apply(context, args);
        }, wait);
    }
}
//防抖立即执行版本
function debounce2(fun, wait) {
    let t;
    return function () {
        let context = this, args = arguments;
        t ? clearTimeout(t) : undefined;
        let callNow = !t;
        t = setTimeout(() => {
           t = null;
        }, wait)
        if (callNow) fun.apply(context, args)
    }
}

//节流时间戳版本
function throttle1(fun, wait) {
    let last = 0;
    return function () {
        let context = this, args = arguments;
        et now = Date.now();
        if (now - last > wait) {
            fun.apply(context, args);
            last = now;
        }
    }
}

//节流定时器版本
function throttle2(fun, wait) {
   let t;
    return function () {
        let context = this, args = arguments;
         if (!t) {
             t = setTimeout(() => {
                 t = null;
                 fun.apply(context, args);
             }, wait)
         }
    }
}