使用JavaScript获取全局变量

- 日理万妓 2023-02-22 03:39 27阅读 0赞

Updated 9/1/2015: My original method, `keys(window)` gave unhelpful results in browsers other than Chrome. I've updated this post with a more reliable method.

2015年9月1日更新：我原来的方法， `keys(window)`在Chrome以外的浏览器中没有帮助。 我已经用更可靠的方法更新了这篇文章。

JavaScript globals are considered bad.  And as a contributor to the MooTools project, I've heard this on a daily basis for the better part of a decade.  MooTools got knocked for extending natives but also for placing objects in the global space, like `Browser` and `$$`.  I find the "global vars are terrible" philosophy a bit funny since even jQuery and JavaScript loaders use a global variable.

JavaScript全局变量被认为是不好的。 作为MooTools项目的贡献者，在过去十年的大部分时间里，我每天都听到这一消息。 MooTools因扩展本机而被淘汰，也因将对象(例如`Browser`和`$$`放置在全局空间中而被淘汰。 我发现“全局变量很糟糕”的哲学有点有趣，因为即使jQuery和JavaScript加载程序也使用全局变量。

Intentional globals aside, leaking global variables is bad practice and a result of sloppy coding.  So how can we see what properties are custom within the global namespace?  It's easier than you think:

除了有意使用全局变量外，泄漏全局变量是一种不好的做法，也是草率编码的结果。 那么，如何查看全局命名空间中自定义的属性呢？ 它比您想象的要容易：

// UPDATE:  This method is too naive
    // Returns an array of window property names
    //keys(window);
    
    // Inject an iframe and compare its `contentWindow` properties to the global window properties
    (function() {
    	var iframe = document.createElement('iframe');
    	iframe.onload = function() {
    		var iframeKeys = Object.keys(iframe.contentWindow);
    		Object.keys(window).forEach(function(key) {
    			if(!(key in iframeKeys)) {
    				console.log(key);
    			}
    		});
    	};
    	iframe.src = 'about:blank';
    	document.body.appendChild(iframe);
    })();

You will see some variables there that you know you didn't set, like `window`, `document`, `top`, and `location`, but the others will have been leaked (or intentional) globals set by custom JavaScript code!

您将在其中看到一些您尚未设置的变量，例如`window` ， `document` ， `top`和`location` ，但是其他变量将被自定义JavaScript代码设置泄漏(或故意)全局变量！

> 翻译自: [https://davidwalsh.name/global-variables-javascript][https_davidwalsh.name_global-variables-javascript]

[https_davidwalsh.name_global-variables-javascript]: https://davidwalsh.name/global-variables-javascript