如何实时获取鼠标的当前坐标

2020-11-27 来源：个人技术集锦

本文来做一个简单的实时获取鼠标坐标的功能，在canvas动画开发中，获取鼠标的坐标，键盘的按键等等，都是常用的操作，我们就慢慢得把他们封装成一个公共库。

一、事件的兼容：

function bindEvent(obj, event, fn) {
 if (obj.attachEvent) { //ie
 obj.attachEvent('on' + event, function () {
 fn.call(obj);
 });
 } else {
 //chrome&ff
 obj.addEventListener(event, fn, false);
 }
 }

上面兼容ie8以及修正this关键字在ie低版本的指向，下面兼容chrome和ff。其他更常用的封装可以参考我的javascript开源框架gdom

二、用立即表达式搭建一个基本的库

添加获取鼠标坐标的方法

;(function (window) {
 window.G = {};
 function bindEvent(obj, event, fn) {
 if (obj.attachEvent) { //ie
 obj.attachEvent('on' + event, function () {
 fn.call(obj);
 });
 } else {
 //chrome&ff
 obj.addEventListener(event, fn, false);
 }
 }

 G.getPos = function( dom ){
 var oPos = { x : 0, y : 0 };
 bindEvent( dom, 'mousemove', function( ev ){
 var oEvent = ev || event, x, y;
 if ( oEvent.pageX || oEvent.pageY ){
 x = oEvent.pageX;
 y = oEvent.pageY;
 }else {
 x = oEvent.clientX + document.body.scrollLeft || document.documentElement.scrollLeft;
 y = oEvent.clientX + document.body.scrollTop || document.documentElement.scrollTop;
 }
 x -= dom.offsetLeft;
 y -= dom.offsetTop;
 oPos.x = x;
 oPos.y = y;
 } );
 return oPos;
 };

})(window);

三、引入封装的js库，绑定canvas为监听对象，打印当前鼠标的坐标

鼠标的坐标，我这里画了2根线，便于观察.

<head>
<meta charset='utf-8' />
<script>
;(function (window) {
 window.G = {};
 function bindEvent(obj, event, fn) {
 if (obj.attachEvent) { //ie
 obj.attachEvent('on' + event, function () {
 fn.call(obj);
 });
 } else {
 //chrome&ff
 obj.addEventListener(event, fn, false);
 }
 }

 G.getPos = function( dom ){
 var oPos = { x : 0, y : 0 };
 bindEvent( dom, 'mousemove', function( ev ){
 var oEvent = ev || event, x, y;
 if ( oEvent.pageX || oEvent.pageY ){
 x = oEvent.pageX;
 y = oEvent.pageY;
 }else {
 x = oEvent.clientX + document.body.scrollLeft || document.documentElement.scrollLeft;
 y = oEvent.clientX + document.body.scrollTop || document.documentElement.scrollTop;
 }
 x -= dom.offsetLeft;
 y -= dom.offsetTop;
 oPos.x = x;
 oPos.y = y;
 } );
 return oPos;
 };

})(window);
</script>
<style>
#canvas{
 border:1px dashed #aaa;
}
</style>
<script>
window.onload = function(){
 var oCanvas = document.querySelector( "#canvas" ),
 oGc = oCanvas.getContext( '2d' ),
 width = oCanvas.width, height = oCanvas.height,
 oInfo = document.querySelector( "#info" ),
 oPos = G.getPos( oCanvas );
 oCanvas.addEventListener( "mousemove", function(){
 
 oGc.clearRect( 0, 0, width, height );
 oGc.beginPath();
 oGc.moveTo( oPos.x, 0 );
 oGc.lineTo( oPos.x, height );
 oGc.moveTo( 0, oPos.y );
 oGc.lineTo( width, oPos.y );
 oGc.closePath();
 oGc.strokeStyle = '#09f';
 oGc.stroke();

 oInfo.innerHTML = '鼠标的当前坐标是:(' + oPos.x + ',' + oPos.y + ')';
 }, false );
}
</script>
</head>
<body>
<canvas id="canvas" width="500" height="400"></canvas>
<p id="info"></p>
</body>

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如何实时获取鼠标的当前坐标