javascript 的惯性运动
2019-05-09 14:36 muamaker 阅读(1047) 评论(0) 编辑 收藏 举报移动端的惯性运动,最早来自 ios 的专利。用于手指滑动,离开屏幕之后,屏幕内容继续滚动。更有动态感。
这里,以 pc 端,鼠标横向(沿x轴) 拖拽的,惯性计算。移动端同理
具体代码如下:
<!DOCTYPE html> <html lang="zh"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>惯性运动</title> <style type="text/css"> #box{ background: pink; width: 100px; height: 100px; position: absolute; top: 100px; left: 100px; } </style> </head> <body> <div id="box"></div> </body> <script type="text/javascript"> var $box = document.getElementById("box"); var isDown = false; //是否按下鼠标 var inertance = 1.2; //惯性系数,越大,惯性越不明显,不能小于0 var fv = 0; //滑动的力度 var timer = null; $box.onmousedown = function(e){ clearTimeout(timer);//清除定时器 fv = 0; this._start = e.clientX; //鼠标按下的位置 isDown = true;//鼠标是否有按下,主要防止用户是从容器外开始滑动的 } $box.onmousemove = function(e){ if(isDown){ var miss = e.clientX - this._start; moveMiss(miss) this._start = e.clientX; fv = miss; } } function moveMiss(miss){ $box.style.left = miss + $box.offsetLeft + "px"; } window.onmouseup = function(e){ if(isDown){ isDown = false; var me = this; var friction = ((fv >> 31) * 2 + 1) * inertance;//根据力度套用公式计算出惯性大小,公式要记住 var num = Math.abs(friction); timer = setInterval(function(){ fv -= friction;//力度按 惯性的大小递减 moveMiss(fv); if(Math.abs(fv) < num){ //如果力度减小到小于1了,结束,或者边界弹回 clearInterval(timer); return ; } },20); } } </script> </html>