有了前面的canvas基础之后，现在开始就精彩了，后面写的canvas教程都是属于综合应用，前面已经写了常用的canvas基础知识,参考链接如下：
[js高手之路] html5 canvas系列教程 - 认识canvas以及基本使用方法
[js高手之路] html5 canvas系列教程 - 掌握画直线图形的常用API
[js高手之路] html5 canvas系列教程 - 开始路径beginPath与关闭路径closePath详解
[js高手之路] html5 canvas系列教程 - arc绘制曲线图形(曲线，弧线，圆形)
[js高手之路] html5 canvas系列教程 - arcTo(弧度与二次,三次贝塞尔曲线以及在线工具)
[js高手之路] html5 canvas系列教程 - 线条样式(lineWidth,lineCap,lineJoin,setLineDash)
[js高手之路] html5 canvas系列教程 - 文本样式(strokeText,fillText,measureText,textAlign,textBaseline)
[js高手之路] html5 canvas系列教程 - 图片操作(drawImage,clip,createPattern)
[js高手之路] html5 canvas系列教程 - 状态详解(save与restore)
[js高手之路] html5 canvas系列教程 - 像素操作(反色,黑白,亮度,复古,蒙版,透明)
[js高手之路] html5 canvas系列教程 - 线形渐变,径向渐变与阴影设置
[js高手之路] html5新增的定时器requestAnimationFrame实战进度条
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：
1 function bindEvent(obj, event, fn) {
2 if (obj.attachEvent) { //ie
3 obj.attachEvent(‘on‘ + event, function () {
4 fn.call(obj);
5 });
6 } else {
7 //chrome&ff
8 obj.addEventListener(event, fn, false);
9 }
10 }
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
1 ;(function (window) {
2 window.G = {};
3 function bindEvent(obj, event, fn) {
4 if (obj.attachEvent) { //ie
5 obj.attachEvent(‘on‘ + event, function () {
6 fn.call(obj);
7 });
8 } else {
9 //chrome&ff
10 obj.addEventListener(event, fn, false);
11 }
12 }
13
14 G.getPos = function( dom ){
15 var oPos = { x : 0, y : 0 };
16 bindEvent( dom, ‘mousemove‘, function( ev ){
17 var oEvent = ev || event, x, y;
18 if ( oEvent.pageX || oEvent.pageY ){
19 x = oEvent.pageX;
20 y = oEvent.pageY;
21 }else {
22 x = oEvent.clientX + document.body.scrollLeft || document.documentElement.scrollLeft;
23 y = oEvent.clientX + document.body.scrollTop || document.documentElement.scrollTop;
24 }
25 x -= dom.offsetLeft;
26 y -= dom.offsetTop;
27 oPos.x = x;
28 oPos.y = y;
29 } );
30 return oPos;
31 };
32
33 })(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.
1 <head>
2 <meta charset=‘utf-8‘ />
3 <script>
4 ;(function (window) {
5 window.G = {};
6 function bindEvent(obj, event, fn) {
7 if (obj.attachEvent) { //ie
8 obj.attachEvent(‘on‘ + event, function () {
9 fn.call(obj);
10 });
11 } else {
12 //chrome&ff
13 obj.addEventListener(event, fn, false);
14 }
15 }
16
17 G.getPos = function( dom ){
18 var oPos = { x : 0, y : 0 };
19 bindEvent( dom, ‘mousemove‘, function( ev ){
20 var oEvent = ev || event, x, y;
21 if ( oEvent.pageX || oEvent.pageY ){
22 x = oEvent.pageX;
23 y = oEvent.pageY;
24 }else {
25 x = oEvent.clientX + document.body.scrollLeft || document.documentElement.scrollLeft;
26 y = oEvent.clientX + document.body.scrollTop || document.documentElement.scrollTop;
27 }
28 x -= dom.offsetLeft;
29 y -= dom.offsetTop;
30 oPos.x = x;
31 oPos.y = y;
32 } );
33 return oPos;
34 };
35
36 })(window);
37 </script>
38 <style>
39 #canvas{
40 border:1px dashed #aaa;
41 }
42 </style>
43 <script>
44 window.onload = function(){
45 var oCanvas = document.querySelector( "#canvas" ),
46 oGc = oCanvas.getContext( ‘2d‘ ),
47 width = oCanvas.width, height = oCanvas.height,
48 oInfo = document.querySelector( "#info" ),
49 oPos = G.getPos( oCanvas );
50 oCanvas.addEventListener( "mousemove", function(){
51
52 oGc.clearRect( 0, 0, width, height );
53 oGc.beginPath();
54 oGc.moveTo( oPos.x, 0 );
55 oGc.lineTo( oPos.x, height );
56 oGc.moveTo( 0, oPos.y );
57 oGc.lineTo( width, oPos.y );
58 oGc.closePath();
59 oGc.strokeStyle = ‘#09f‘;
60 oGc.stroke();
61
62 oInfo.innerHTML = ‘鼠标的当前坐标是:(‘ + oPos.x + ‘,‘ + oPos.y + ‘)‘;
63 }, false );
64 }
65 </script>
66 </head>
67 <body>
68 <canvas id="canvas" width="500" height="400"></canvas>
69 <div id="info"></div>
70 </body>
四、点击‘run code‘可以预览效果额
<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>
<div id="info"></div>
</body>
run code