Javascript 覆盖函数（例如“警报”）并调用原始函数？
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Override function (e.g. "alert") and call the original function?
提问by Rob W
I would like to override a Javascript built-in function with a new version that calls the original (similarly to overriding a method on a class with a version that calls superin many languages). How can I do this?
我想用一个调用原始函数的新版本来覆盖一个 Javascript 内置函数（类似于用一个super以多种语言调用的版本覆盖一个类上的方法）。我怎样才能做到这一点？
For example...
例如...
window.alert = function(str) {
//do something additional
if(console) console.log(str);
//super.alert(str) // How do I do this bit?
}
回答by Rob W
Store a reference to the original function in a variable:
将原始函数的引用存储在变量中：
(function() {
var _alert = window.alert; // <-- Reference
window.alert = function(str) {
// do something additional
if(console) console.log(str);
//return _alert.apply(this, arguments); // <-- The universal method
_alert(str); // Suits for this case
};
})();
The universal way is <original_func_reference>.apply(this, arguments)- To preserve context and pass all arguments. Usually, the return value of the original method should also be returned.
通用方法是<original_func_reference>.apply(this, arguments)- 保留上下文并传递所有参数。通常，原始方法的返回值也应该返回。
However, it's known that alertis a void function, takes only one argument, and does not use the thisobject. So, _alert(str)is sufficient in this case.
然而，众所周知它alert是一个空函数，只接受一个参数，并且不使用this对象。所以，_alert(str)在这种情况下就足够了。
Note: IE <= 8 throws an error if you try to overwrite alert, so make sure that you're using window.alert = ...instead of alert = ....
注意：如果您尝试覆盖 IE <= 8 会引发错误alert，因此请确保您使用的是window.alert = ...而不是alert = ....
回答by Rob W
There is no "super". Anyway, create a closure to "keep" around the original function-object.
没有“超级”。无论如何，创建一个闭包来“保留”原始函数对象。
Note the "self invoking function" that returns a new function-object (that is assigned to the window.alertproperty). The new function-object returned creates a closure around the variableoriginalwhich evaluates to the original valueof window.alertthat was passed in to the "self invoking function".
请注意“自调用函数”，它返回一个新的函数对象（分配给window.alert属性）。返回的新函数对象周围产生一个闭合变量original，其计算结果为原始值的window.alert，在“自主调用功能”获得通过。
window.alert = (function (original) {
return function (str) {
//do something additional
if(console) {
console.log(str)
}
original(str)
}
})(window.alert)
However, I believesome browsers may prevent alertand other built-ins from being modified...
但是，我相信某些浏览器可能会阻止alert和其他内置程序被修改...
Happy coding.
快乐编码。
回答by Art
I'm assuming your question is how do you overwrite a built-in and still be able to call it. First off as a disclaimer, you should never overwrite built ins unless you have a good reason for doing it since it will make it impossible to debug/test.
我假设您的问题是如何覆盖内置函数并仍然能够调用它。首先作为免责声明，除非您有充分的理由这样做，否则您永远不应该覆盖内置插件，因为它会使调试/测试变得不可能。
This is how you would do it:
这是你会怎么做：
window._alert = window.alert;
window.alert = function(str) {
if(console) console.log(str);
window._alert(str);
}
回答by Poul Krogh
How to do simple classical inheritance in Javascript:
如何在 Javascript 中进行简单的经典继承：
SuperClass.call(this) // inherit from SuperClass (multiple inheritance yes)
How to override functions:
如何覆盖函数：
this.myFunction = this.myFunction.override(
function(){
this.superFunction(); // call the overridden function
}
);
The override function is created like this:
覆盖函数是这样创建的：
Function.prototype.override = function(func)
{
var superFunction = this;
return function()
{
this.superFunction = superFunction;
return func.apply(this,arguments);
};
};
Works with multiple arguments.
Fails when trying to override undefined or nonfunctions.
Makes "superFunction" a "reserved" word :-)
适用于多个参数。
尝试覆盖未定义或非函数时失败。
使“superFunction”成为“保留”字:-)
回答by David M
JavaScript does not use a classical inheritance model. There is a nice article herewhich describes a way to write your classes so that a similar syntax can be used, but it's not natively supported.
JavaScript 不使用经典的继承模型。这里有一篇很好的文章，它描述了一种编写类的方法，以便可以使用类似的语法，但它本身并不支持。
