Javascript:非法调用 [英] Javascript: Illegal invocation

问题描述

我遇到了一个问题.我正在使用一个具有以下逻辑的相当老的应用程序:

I am experiencing an issue. I am working with a fairly old application which has the following logic:

var Page;
var OriginalSubmit;

function init() {
    Page = document.forms[0];
    OriginalSubmit = Page.submit;
    Page.submit = newPageSubmit;
}

function newPageSubmit() {
  validate();
  OriginalSubmit();
}

当执行OriginalSubmit时，我得到一个非法调用参数.我已经读够了，这是因为此引用已更改(至少我认为是这种情况)，但是我正在努力解决的是正确的方法.为此，JavaScript很混乱，到处都是JSP和全局函数，因此要使其正确将是一项艰巨的工作，因此，我很想看看是否有可能采用侵入性较小的解决方案，谢谢.

When the OriginalSubmit is executed, I get an Illegal invocation argument. I've read enough to understand that is because the this reference has changed (at least I think that's the case), but what I am struggling with is the correct way to fix it. The JavaScript for this is a mess, wrapped up with JSPs and global functions everywhere, so making this correct would be quite an effort, so I am looing to see if there's a chance for a less invasive solution, thanks.

推荐答案

分配OriginalSubmit = Page.submit时，您会获得对.submit()函数的引用，但是当您将其仅作为普通OriginalSubmit()调用时，丢失Page上下文变量，该上下文变量将作为this传递给该函数:

When you assign OriginalSubmit = Page.submit you're obtaining a reference to the .submit() function, but when you call it as just plain OriginalSubmit() you're losing the Page context variable that will be passed as this to that function:

myObject.method();  // calls "method" with "this === myObject"

var method = myObject.method();
method();           // calls "method" with "this === window"

相反，请使用:

OriginalSubmit.call(Page);    // sets "this" to "Page"

请注意，即使那样，重新分配本机DOM元素的方法也可能无法在所有浏览器中移植，并且可能根本无法使用.

Note that even then, it's possible that re-assigning a method of a native DOM element won't work portably in all browsers, and may not work at all.

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