在WebKit中使用本机代码函数作为JavaScript对象 [英] Using native code functions as JavaScript objects in WebKit
问题描述
我无法在基于WebKit的浏览器中将本机代码函数用作JavaScript对象。是不是可以直接别名这些功能?
I'm unable to use native code functions as JavaScript objects in WebKit-based browsers. Is it impossible to alias these functions directly?
这是最容易通过示例解释的,所以这是我在Developer Tools控制台中运行的内容:
This is easiest to explain by example, so here is what I am running in the Developer Tools console:
console.warn;
// Outputs:
// function warn() {
// [native code]
// }
console.warn("console.warn");
// Outputs: "console.warn"
var _c = console;
_c.warn("_c.warn");
// Outputs: "_c.warn"
var _w = console.warn;
_w("_w");
// Outputs: "TypeError: Type error" on Safari/WebKit (Mac)
// Outputs: "TypeError: Illegal invocation" on Chrome (Mac)
var _w2 = function () { console.warn.apply(console, arguments); }
_w2("_w2");
// Outputs: "w2"
当我尝试在Safari中使用 jQuery Lint 时出现了这个问题;如果window.console不存在,它使用以下方法来防止破坏:
This issue came up as I tried to use jQuery Lint in Safari; it uses the following approach to prevent breakage if window.console does not exist:
_console = {
warn: window.console && console.warn || function(){},
...
}
_console.warn("some error");
这是我的临时解决方法:
Here's my temporary workaround:
if((jQuery.browser.safari || jQuery.browser.webkit) && window.console) {
jQuery.LINT.level = 3;
jQuery.LINT.console = {
warn: function() { console.warn.apply(console, arguments); },
group: function() { console.group.apply(console, arguments); },
groupEnd: function() { console.groupEnd(); },
groupCollapsed: function() { console.group.apply(console, arguments); },
log: function() { console.log.apply(console, arguments); }
}
}
推荐答案
您不能在JavaScript中替换任何方法,无论是否为本机,WebKit或不是。
You can't alias any methods in JavaScript, native or not, WebKit or not.
当您说 var时_w = console.warn;
,你正在剥离警告
远离其所有者对象 console
并将其视为一个独立的功能。当你调用它时,它没有这个
对
控制台
的引用,所以它无法工作。
When you say var _w = console.warn;
, you are stripping warn
away from its owner object console
and treating it as a standalone function. When you call it, it gets no this
reference to the console
, so it fails to work.
您可能会发现绑定方法在其他语言中的工作方式有所不同,但这就是JavaScript方法调用的设计方式: this
引用仅基于所有者
在 owner.method()
(或<$ c $)中的函数传递给函数C>所有者[ '方法']())。如果在没有所有者的情况下单独调用该函数,此
设置为窗口
对象,该方法很可能会下降结束。
You may find this unusual from how bound methods work in other languages, but that's just how JavaScript method calls are designed: the this
reference is passed to a function based solely on what owner
is in owner.method()
(or owner['method']()
). If the function is called alone without an owner, this
is set to the window
object and the method will most likely fall over.
要解决此问题并传入正确的此
,您必须使用 method.call
(或 method.apply
)显式地由@slebetman描述,或者使用像<$ c这样的闭包创建自己的绑定函数$ c> var _w = function(){console.warn.apply(console,arguments)}; 或者,在ECMAScript第五版中, method.bind(所有者)
。
To get around this and pass in a proper this
, you must either use method.call
(or method.apply
) explicitly as described by @slebetman, or make your own bound function using a closure like var _w= function() { console.warn.apply(console, arguments) };
or, in ECMAScript Fifth Edition, method.bind(owner)
.
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