Canvas统计图插件编写实例(2)

(function(){ var lastTime = 0; var prefixes = ['ms','webkit','o','moz']; //各浏览器前缀 var requestAnimationFrame = window.requestAnimationFrame; var cancelAnimationFrame = window.cancelAnimationFrame; var prefix; //通过遍历各浏览器前缀，来得到requestAnimationFrame和cancelAnimationFrame在当前浏览器的实现形式 for( var i = 0; i < prefixes.length; i++ ) { if ( requestAnimationFrame && cancelAnimationFrame ) { break; } prefix = prefixes[i]; requestAnimationFrame = requestAnimationFrame || window[ prefix + 'RequestAnimationFrame' ]; cancelAnimationFrame = cancelAnimationFrame || window[ prefix + 'CancelAnimationFrame' ] || window[ prefix + 'CancelRequestAnimationFrame' ]; } //如果当前浏览器不支持requestAnimationFrame和cancelAnimationFrame，则会退到setTimeout if ( !requestAnimationFrame || !cancelAnimationFrame ) { requestAnimationFrame = function( callback, element ) { var currTime = new Date().getTime(); //为了使setTimteout的尽可能的接近每秒60帧的效果 var timeToCall = Math.max( 0, 16 - ( currTime - lastTime ) ); var id = window.setTimeout( function() { callback( currTime + timeToCall ); }, timeToCall ); lastTime = currTime + timeToCall; return id; }; cancelAnimationFrame = function( id ) { window.clearTimeout( id ); }; } window.requestAnimationFrame = requestAnimationFrame; window.cancelAnimationFrame = cancelAnimationFrame; }());

附上<script>调用