JS实现用键盘控制DIV上下左右+放大缩小与变色

时间：2021-05-14 19:20:16
<!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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