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当鼠标按下时拖动元素，简单的JS实现

  • 友人a丶
  • JS笔记
  • 2021-07-28
  • 1075热度
  • 0评论

记录

监听需要移动元素的键盘按下、松开事件和文档对象的鼠标移动事件，

通过一个布尔值作为是否移动的标志，按下时为TRUE，代表跟随移动，鼠标松开为FALSE，代表不跟随移动，鼠标移动时改变元素偏移量。

<!DOCTYPE html>
<html lang="en">
<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>物体跟着鼠标移动</title>
</head>
<style>
    .box {
        width: 100px;
        height: 100px;
        background-color: red;
        position: absolute;
        left: 0;
        top: 0;
    }
</style>
<body>
    <div class="box"></div>
</body>
<script>
     var boxDom = document.querySelector(".box");
     var flag=false,offX,offY;
     boxDom.onmousedown=function (){
         let evt = event || window.event;
         offX=evt.clientX-window.getComputedStyle(boxDom,null)["left"].slice(0,-2);
         offY=evt.clientY-window.getComputedStyle(boxDom,null)["top"].slice(0,-2);
         flag=true;
     }
     boxDom.onmouseup=function (){
         flag=false;
     }
     document.onmousemove = function (event) {
         if(flag){
             let evt = event || window.event;
             console.log(evt.clientX -offX);
             console.log(evt.clientY - offY);
             boxDom.style.left = evt.clientX -offX + "px";
             boxDom.style.top = evt.clientY - offY + "px";
         }
     }
 </script>
 </html>