變速動畫函數封裝 · js技術點

```html <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>title</title> <style> * { margin: 0; padding: 0; } div { margin-top: 20px; width: 200px; height: 100px; background-color: green; position: absolute; left: 0; top: 0; } </style> </head> <body> <input type="button" value="移動到400px" id="btn1"/> <input type="button" value="移動到800px" id="btn2"/> <div id="dv"></div> <script src="common.js"></script> <script> //點擊按鈕移動div my$("btn1").onclick = function () { animate(my$("dv"), 400); }; my$("btn2").onclick = function () { animate(my$("dv"), 800); }; //變速動畫 function animate(element, target) { //清理定時器 clearInterval(element.timeId); element.timeId = setInterval(function () { //獲取元素的當前位置 var current = element.offsetLeft; //移動的步數 var step = (target-current)/10; // Math.ceil是四舍五入，Math.floor是去下界 step = step > 0 ? Math.ceil(step) : Math.floor(step); current += step; element.style.left = current + "px"; if(current == target) { //清理定時器 clearInterval(element.timeId); } //測試代碼: console.log("目標位置:"+target+",當前位置:"+current+",每次移動步數:"+step); }, 20); } </script> </body> </html> ```