匀速运动的封装 

    function animate(obj,endPosition,speed) {
        clearInterval(obj.timer);
        var speed = obj.offsetLeft > endPosition ? -speed : speed;
        obj.timer = setInterval(function () {
            var judgeDot = Math.abs(obj.offsetLeft - endPosition);
            obj.style.left = obj.offsetLeft + speed + 'px';//judgeDot changes with this interval.So this sentence should be in the interval;
            if(judgeDot <= Math.abs(speed)) {
                clearInterval(obj.timer);
                obj.style.left = endPosition + 'px';
            }
        },30);
    }
//obj是将要做运动的对象，有position属性的对象，endPosition对是向右运动的最远距离时的left值，speed是运动速度。

 案例如下：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #box {width: 100px; height: 100px; background: #dfd; position: absolute; top: 150px; left: 56px;}
    </style>
</head>
<body>
<button id="b1">200</button>
<button id="b2">400</button>
    <div id="box"></div>
</body>
</html>
<script>
    var box = document.getElementById('box');
    var b1 = document.getElementById('b1');
    var b2 = document.getElementById('b2');
    b1.onclick = function () {
        animate(box,200,10);
    }
    b2.onclick = function () {
        animate(box,400,10);
    }
    function animate(obj,endPosition,speed) {
        clearInterval(obj.timer);
        var speed = obj.offsetLeft > endPosition ? -speed : speed;
        obj.timer = setInterval(function () {
            var judgeDot = Math.abs(obj.offsetLeft - endPosition);
            obj.style.left = obj.offsetLeft + speed + 'px';//judgeDot changes with this interval.So this sentence should be in the interval;
            if(judgeDot <= Math.abs(speed)) {
                clearInterval(obj.timer);
                obj.style.left = endPosition + 'px';
            }
        },30);
    }
</script>

 

posted @ 2016-12-23 10:28  ifIhaveWings  阅读(154)  评论(0)  编辑  收藏  举报