关于如何优化jQuery的实例详解

而我们想要的明显是在结束调整之后才执行事件。幸运的是我们可以通过以下几种方法来调整。

jQuery惰性插件

jQuery throttle / debounce: Sometimes, less is more!

(function(b,c){var $=b.jQuery||b.Cowboy||(b.Cowboy={}),a;$.throttle=a=function(e,f,j,i){var h,d=0;if(typeof f!=="boolean"){i=j;j=f;f=c}function g(){var o=this,m=+new Date()-d,n=arguments;function l(){d=+new Date();j.apply(o,n)}function k(){h=c}if(i&&!h){l()}h&&clearTimeout(h);if(i===c&&m>e){l()}else{if(f!==true){h=setTimeout(i?k:l,i===c?e-m:e)}}}if($.guid){g.guid=j.guid=j.guid||$.guid++}return g};$.debounce=function(d,e,f){return f===c?a(d,e,false):a(d,f,e!==false)}})(this);

使用方法：

function log( event ) {
 console.log( $(window).scrollTop(), event.timeStamp );
};

// Console logging happens on window scroll, WAAAY more often
// than you want it to.
$(window).scroll( log );

// Console logging happens on window scroll, but no more than
// once every 250ms.
$(window).scroll( $.throttle( 250, log ) );

// Note that in jQuery 1.4+ you can unbind by reference using
// either the throttled function, or the original function.
$(window).unbind( 'scroll', log );

JS代码

(function($,sr){

// debouncing function from John Hann
// http://unscriptable.com/index.php/2009/03/20/debouncing-javascript-methods/
var debounce = function (func, threshold, execAsap) {
var timeout;

return function debounced () {
var obj = this, args = arguments;
function delayed () {
if (!execAsap)
func.apply(obj, args);
timeout = null;
};

if (timeout)
clearTimeout(timeout);
else if (execAsap)
func.apply(obj, args);

timeout = setTimeout(delayed, threshold || 100);
};
}
// smartresize
jQuery.fn[sr] = function(fn){ return fn ? this.bind('resize', debounce(fn)) : this.trigger(sr); };

})(jQuery,'smartresize');
// usage:
$(window).smartresize(function(){
// code that takes it easy...
});

总结起来第一种简单容易理解，第二种则是比较全面，代码也少，第三种也差不多。

javascript-resize-performance/

第二种：benalman.com/projects/jquery-throttle-debounce-plugin/

第三种：www.paulirish.com/2009/throttled-smartresize-jquery-event-handler/

JavaScript代码：unscriptable.com/2009/03/20/debouncing-javascript-methods/

以后对于滚动、调整窗体大小等最好使用这种方法来减少JavaScript执行的次数。慎记。