【转载】jQuery源码分析-06浏览器测试-Support

rwebkit = /(webkit)[ /]([w.]+)/,

ropera = /(opera)(?:.*version)?[ /]([w.]+)/,

rmsie = /(msie) ([w.]+)/,

rmozilla = /(mozilla)(?:.*? rv:([w.]+))?/,

// 到处都是把属性取出来，作为局部变量使用，可以减少跨作用域查询，提高性能

userAgent = navigator.userAgent,

// 用户代理匹配结果

browserMatch,

ua = ua.toLowerCase();

// 依次匹配各浏览器

var match = rwebkit.exec( ua ) ||

ropera.exec( ua ) ||

rmsie.exec( ua ) ||

ua.indexOf(“compatible”) < 0 && rmozilla.exec( ua ) ||

[];

// match[1] || “” ：match[1]为false（空字符串、null、undefined、0等）时，默认为””

// match[2] || “0” ：match[2]为false（空字符串、null、undefined、0等）时，默认为”0″

return { browser: match[1] || “”, version: match[2] || “0” };},

if ( browserMatch.browser ) {

jQuery.browser[ browserMatch.browser ] = true;

jQuery.browser.version = browserMatch.version;

}

// 不推荐使用safari标记，用webkit代替

if ( jQuery.browser.webkit ) {

jQuery.browser.safari = true;

}

// Use the handy event callback

// 使用较快的加载完毕事件

document.addEventListener( “DOMContentLoaded”, DOMContentLoaded, false );

// A fallback to window.onload, that will always work

// 注册window.onload回调函数

window.addEventListener( “load”, jQuery.ready, false );

// If IE event model is used

// 如果是IE事件模型

} else if ( document.attachEvent ) {

// ensure firing before onload,

// maybe late but safe also for iframes

// 确保在onload之前触发onreadystatechange，可能慢一些但是对iframes更安全

document.attachEvent( “onreadystatechange”, DOMContentLoaded );

// A fallback to window.onload, that will always work

// 注册window.onload回调函数

window.attachEvent( “onload”, jQuery.ready );

// If IE and not a frame

// continually check to see if the document is ready

var toplevel = false;

try {

toplevel = window.frameElement == null;

} catch(e) {}

if ( document.documentElement.doScroll && toplevel ) {

doScrollCheck();

}

}