JavaScript强化教程――DOM编程（两种控制div移动的方法）

程序员文章站 2022-05-08 16:45:53

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第一种按钮控制
首先创建两个html按钮和一个div并给div一个样式

input type="button" value="左" id="1">
<input type="button" value="右" id="2">
<div id="3">
div {
            width: 100px;
            height: 100px;
            background-color: bisque;
            position: absolute;
            left: 100px;
            top: 100px;
        }

然后在script中获得div和两个按钮

var left = document.getElementById("2");
    var right = document.getElementById("1");
    var div = document.getElementById("3");

然后添加onclick函数

left.onclick = function () {
           
    }
    right.onclick = function () {
      
    }

设置一个变量，控制div的left改变

var x = 100;

当点击按钮时触发

left.onclick = function () {
            x=x+10;
            div.style.left = x+"px";
    }
    right.onclick = function () {
        x=x-10;
        div.style.left = x+"px";
    }

源码：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
       div {             width: 100px;             height: 100px;             background-color: bisque;      
              position: absolute;             left: 100px;             top: 100px;         }
    </style>
</head>
<body>
<input type="button" value="左" id="1"> <input type="button" value="右" id="2"> <div id="3"> </div>

<script>
    var left = document.getElementById("2");     var right = document.getElementById("1");    
     var div = document.getElementById("3");
    var x = 100;
    left.onclick = function () {             x=x+10;             div.style.left = x+"px";   
      }     right.onclick = function () {         x=x-10;         div.style.left = x+"px";     }

</script>

</body>
</html>

第二种，键值控制
同样在html中创建div并给其样式

<div id="3">
</div>
<style>
       div {
            width: 100px;
            height: 100px;
            background-color: bisque;
            position: absolute;
            left: 100px;
            top: 100px;
        }
    </style>

在script里面获得div

var div=document.getElementById("3");

然后声明两个变量控制改变div的left和top

var px=100;
 var py =100;

然后获得键值
document.onkeydown（在document文档对象中，按任何键都会触发此函数）
alert中输出的event.keyCode会对应按键时，当前键相应的事件值（即每一个按键对应为一个键值）

document.onkeydown = function(){
        alert(event.keyCode);
}

然后通过测试上下左右得到键值，在swich语句中改变div的left和top改变其位置

switch (event.keyCode){
            case 37:
            px = px-10;
            div.style.left = px+"px";
                break;
            case 38:
                py = py-10;
                div.style.top = py+"px";
                break;
            case 39:
                px = px+10;
                div.style.left = px+"px";
                break;
            case 40:
                py = py+10;
                div.style.top = py+"px";
                break;
        }

源码：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
       div {             width: 100px;             height: 100px;            
        background-color: bisque;             position: absolute;             left: 100px;            
         top: 100px;         }
    </style>
</head>
<body>

<div id="3"> </div>

<script>

    var div=document.getElementById("3");
    var px=100;
    var py =100;
    document.onkeydown = function(){
//        alert(event.keyCode);
        switch (event.keyCode){             case 37:             px = px-10;            
         div.style.left = px+"px";                 break;             case 38:                
          py = py-10;                 div.style.top = py+"px";                 break;           
            case 39:                 px = px+10;                 div.style.left = px+"px";                
             break;             case 40:                 py = py+10;                 div.style.top = py+"px";                 break;         }
    }

</script>

</body>
</html>

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