js 闭包

通过闭包封装私有变量

function a() {
    //函数外访问不到
    var s = 3;
   //使外部能够获得s变量的值 
    this.f = function () {
        return s
    }
    //改变s的值
    this.add=function(){
        s++
    }
}

var t = new a()
t.add()
console.log(t.f())

通过回调函数，每个方法拥有独立的私有变量

    <div id="box1">box1</div>
    <div id="box2">box2</div>
    <script>
        function ani(elementId) {
            var elem = document.getElementById(elementId)
            console.log(elem.style)
            var count = 0
            var timer = setInterval(function () {
                if (count < 100) {
                    elem.style.margin = count + "px"
                    count++
                    console.log(elem.style.left)
                } else {
                    clearInterval(timer)
                }
            }, 10)
        }
        ani("box1")
        ani("box2")
    </script>