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.《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》

《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》