JavaScript函数别名似乎不工作 [英] JavaScript function aliasing doesn't seem to work
问题描述
我只是在阅读这个问题，想尝试别名方法，而不是函数包装器方法，但我似乎无法使它工作在Firefox 3或3.5beta4或谷歌Chrome，无论是在他们的调试窗口和测试网页。
I was just reading this question and wanted to try the alias method rather than the function-wrapper method, but I couldn't seem to get it to work in either Firefox 3 or 3.5beta4, or Google Chrome, both in their debug windows and in a test web page.
Firebug：
>>> window.myAlias = document.getElementById
function()
>>> myAlias('item1')
>>> window.myAlias('item1')
>>> document.getElementById('item1')
<div id="item1">
如果我把它放在网页中，调用myAlias会给我这个错误：
If I put it in a web page, the call to myAlias gives me this error:
uncaught exception: [Exception... "Illegal operation on WrappedNative prototype object" nsresult: "0x8057000c (NS_ERROR_XPC_BAD_OP_ON_WN_PROTO)" location: "JS frame :: file:///[...snip...]/test.html :: <TOP_LEVEL> :: line 7" data: no]
Chrome（为了清楚起见，插入了>>>）：
Chrome (with >>>'s inserted for clarity):
>>> window.myAlias = document.getElementById
function getElementById() { [native code] }
>>> window.myAlias('item1')
TypeError: Illegal invocation
>>> document.getElementById('item1')
<div id=?"item1">?
在测试页面中，我得到了相同的非法调用。
And in the test page, I get the same "Illegal invocation".
我做错了什么？
此外，奇怪的是，我只是试过，它在IE8中工作。
Also, oddly enough, I just tried and it works in IE8.
推荐答案
您必须将该方法绑定到文档对象。看：
You have to bind that method to the document object. Look:
>>> $ = document.getElementById
getElementById()
>>> $('bn_home')
[Exception... "Cannot modify properties of a WrappedNative" ... anonymous :: line 72 data: no]
>>> $.call(document, 'bn_home')
<body id="bn_home" onload="init();">
当你做一个简单的别名时，函数会在全局对象上调用，而不是在文档对象。使用一种名为closures的技术来解决这个问题：
When you’re doing a simple alias, the function is called on the global object, not on the document object. Use a technique called closures to fix this:
function makeAlias(object, name) {
var fn = object ? object[name] : null;
if (typeof fn == 'undefined') return function () {}
return function () {
return fn.apply(object, arguments)
}
}
$ = makeAlias(document, 'getElementById');
>>> $('bn_home')
<body id="bn_home" onload="init();">
这样就不会丢失对原始对象的引用。
This way you don’t loose the reference to the original object.
在2012年，有一个新的 bind 方法从ES5允许我们以一个鸽友的方式：
In 2012, there is the new bind method from ES5 that allows us to do this in a fancier way:
>>> $ = document.getElementById.bind(document)
>>> $('bn_home')
<body id="bn_home" onload="init();">
这篇关于JavaScript函数别名似乎不工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
