Prototype 学习 Prototype对象
2024-05-06 14:14:52
供稿：网友
环境：
Prototype Version: '1.6.1_rc3'
Aptana Studio, build: 1.2.5.023247
IE7
FF2.0.0.4
Opera 10 beta
代码如下:
var Prototype = {
Version: '1.6.1_rc3',
//定义浏览器对象
Browser: (function(){
var ua = navigator.userAgent;
var isOpera = Object.prototype.toString.call(window.opera) == '[object Opera]';
return {
IE: !!window.attachEvent && !isOpera,
Opera: isOpera,
WebKit: ua.indexOf('AppleWebKit/') > -1,
Gecko: ua.indexOf('Gecko') > -1 && ua.indexOf('KHTML') === -1,
MobileSafari: /Apple.*Mobile.*Safari/.test(ua)
}
})(),
//定义浏览器Feature对象
BrowserFeatures: {
XPath: !!document.evaluate,
SelectorsAPI: !!document.querySelector,
ElementExtensions: (function() {
var constructor = window.Element || window.HTMLElement;
return !!(constructor && constructor.prototype);
})(),
SpecificElementExtensions: (function() {
if (typeof window.HTMLDivElement !== 'undefined')
return true;
var div = document.createElement('div');
var form = document.createElement('form');
var isSupported = false;
if (div['__proto__'] && (div['__proto__'] !== form['__proto__'])) {
isSupported = true;
}
div = form = null;
return isSupported;
})()
},
ScriptFragment: '<script[^>]*>([//S//s]*?)<//script>',
JSONFilter: /^///*-secure-([/s/S]*)/*///s*$/,
emptyFunction: function() { },
K: function(x) { return x }
};
if (Prototype.Browser.MobileSafari)
Prototype.BrowserFeatures.SpecificElementExtensions = false;
Broswer对象是通过调用匿名函数并且立即执行的方式返回的，执行匿名函数的方法有三种：
1. (function(){return 1})() //()可以强制求值，返回函数对象然后执行函数
2. (function(){return 1}()) //返回函数执行的结果
3. void function(){alert(1)}() //void 也有强制运算的用法
其中判断Opera的方法isOpera用到了window.opera，在Opera浏览器中会返回一个对象，其它浏览器返回undefined
BrowserFeatures对象主要判断浏览器的一些特性，FF支持许多的特性在IE下不支持，比如document.evalute方法就可以通过XPATH的方式操作HTML文档，但IE就不支持。
此函数详细用法如下：
代码如下:
var xpathResult = document.evaluate(xpathExpression, contextNode, namespaceResolver, resultType, result);
The evaluate function takes a total of five arguments:
xpathExpression: A string containing an xpath expression to be evaluated
contextNode: A node in the document against which the Xpath expression should be evaluated
namespaceResolver: A function that takes a string containing a namespace prefix from the xpathExpression and returns a string containing the URI to which that prefix corresponds. This enables conversion between the prefixes used in the XPath expressions and the (possibly different) prefixes used in the document
resultType: A numeric constant indicating the type of result that is returned. These constants are avaliable in the global XPathResult object and are defined in the relevaant section of the XPath Spec. For most purposes it's OK to pass in XPathResult.ANY_TYPE which will cause the results of the Xpath expression to be returned as the most natural type
