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JS实现用键盘控制DIV上下左右+放大缩小与变色

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>用键盘控制DIV</title> 
<style type="text/css"> 
html,body{overflow:hidden;} 
body{margin:0;padding:0;} 
pre{
    color:green;
    padding:10px 15px;
    background:#f0f0f0;
    border:1px dotted #333;
    font:12px/1.5 Courier New;
    margin:12px;
} 
span{color:#999;} 
#box{
    position:absolute;
    top:50px;
    left:300px;
    width:100px;
    height:100px;
    background:red;
} 
</style> 
<script type="text/javascript"> 
window.onload = function () { 
    var oBox = document.getElementById("box"); 
    var bLeft = bTop = bRight = bBottom = bCtrlKey = false; 

    setInterval(function (){ 
        if (bLeft){ 
            oBox.style.left = oBox.offsetLeft - 10 + "px" 
        }else if (bRight) { 
            oBox.style.left = oBox.offsetLeft + 10 + "px" 
        }
        if (bTop){ 
            oBox.style.top = oBox.offsetTop - 10 + "px" 
        }else if(bBottom){ 
            oBox.style.top = oBox.offsetTop + 10 + "px" 
        } 
        //防止溢出 
        limit(); 
    },30); 

    document.onkeydown = function (event) 
    { 
        var event = event || window.event; 
        bCtrlKey = event.ctrlKey; 
    
        switch (event.keyCode) { 
            case 37: 
                bLeft = true; 
                break; 
            case 38: 
                //放大
                if(bCtrlKey){ 
                    var oldWidth = oBox.offsetWidth; 
                    var oldHeight = oBox.offsetHeight; 
                    oBox.style.width = oBox.offsetWidth * 1.5 + "px"; 
                    oBox.style.height = oBox.offsetHeight * 1.5 + "px"; 
                    oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px"; 
                    oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px"; 
                    break; 
                } 
                bTop = true; 
                break; 
            case 39: 
                bRight = true; 
                break; 
            case 40: 
                if(bCtrlKey) { 
                    var oldWidth = oBox.offsetWidth; 
                    var oldHeight = oBox.offsetHeight; 
                    oBox.style.width = oBox.offsetWidth * 0.75 + "px"; 
                    oBox.style.height = oBox.offsetHeight * 0.75 + "px"; 
                    oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px"; 
                    oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";     
                    break; 
                } 
                bBottom = true; 
                break; 
            case 49: 
                bCtrlKey && (oBox.style.background = "green"); 
                break; 
            case 50: 
                bCtrlKey && (oBox.style.background = "yellow"); 
                break; 
            case 51: 
                bCtrlKey && (oBox.style.background = "blue"); 
                break; 
            } 
            return false 
    }; 
    document.onkeyup = function (event) { 
        switch ((event || window.event).keyCode){ 
            case 37: 
                bLeft = false; 
                break; 
            case 38: 
                bTop = false; 
                break; 
            case 39: 
                bRight = false; 
                break; 
            case 40: 
                bBottom = false; 
                break; 
        } 
    }; 
    //防止溢出 
    function limit() { 
        var doc = [document.documentElement.clientWidth, document.documentElement.clientHeight] 
        //防止左侧溢出 
        oBox.offsetLeft <=0 && (oBox.style.left = 0); 
        //防止顶部溢出 
        oBox.offsetTop <=0 && (oBox.style.top = 0); 
        //防止右侧溢出 
        doc[0] - oBox.offsetLeft - oBox.offsetWidth <= 0 && (oBox.style.left = doc[0] - oBox.offsetWidth + "px"); 
        //防止底部溢出 
        doc[1] - oBox.offsetTop - oBox.offsetHeight <= 0 && (oBox.style.top = doc[1] - oBox.offsetHeight + "px") 
    } 
}; 
</script> 
</head> 
<body> 
<pre> 
红色方块为键盘操作区域，您可以进行如下操作： 
上：↑ 下：↓ 左：← 右：→ 
Ctrl + 1 : 背景变为绿色 
Ctrl + 2 : 背景变为黄色 
Ctrl + 3 : 背景变为蓝色 
Ctrl + ↑ : 放大 
Ctrl + ↓ : 缩小 
</pre> 
<div id="box"></div> 
</body> 
</html>

摘自：http://www.jb51.net/article/32823.htm

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原文地址：https://www.cnblogs.com/MY0101/p/6129808.html