window[] 和 eval() 之间的区别 - Javascript
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Difference between window[] and eval() - Javascript
提问by Norman
I've been using both in javascript ... really don't know the difference. Googling always shows results for the "window object" or "opening a new window in javascript" so couldn't find anything there.
我一直在 javascript 中使用两者......真的不知道有什么区别。谷歌搜索总是显示“窗口对象”或“在 javascript 中打开一个新窗口”的结果，所以在那里找不到任何东西。
eval("v"+e)
window["v"+e]
Sometimes window works for me and at other times eval works ....
有时 window 对我有用，有时 eval 对我有用....
So what's the difference between eval() and window[] ?
那么 eval() 和 window[] 之间有什么区别？
Sorry for the newbie question though !
对不起，新手问题！
Norman
诺曼
回答by CMS
Another point that has not been addressed is that evalwill resolve the variable reference using the caller variable environment, for example:
另一个尚未解决的问题是eval将使用调用者变量 environment解析变量引用，例如：
var foo = "global";
(function () {
var foo = "local";
alert(eval("foo")); // alerts "local"
alert(window["foo"]); // alerts "global"
})();
So as you can see, is not completely equivalent.
正如你所看到的， 并不完全等效。
If you simply want to reference a global variable, I would recommend you to use the window[prop]approach and avoid surprises.
如果您只是想引用一个全局变量，我建议您使用该window[prop]方法并避免意外。
回答by Paul Grime
eval() interprets arbitrary javascript statements, whereas with window you are accessing a property of the window object.
eval() 解释任意 javascript 语句，而使用 window 您正在访问 window 对象的属性。
In your example, you seem to be using a property name in both eval() and window[]. As the global scope in a browser is the same as the window object's scope they will evaluate to the same thing.
在您的示例中，您似乎在 eval() 和 window[] 中都使用了属性名称。由于浏览器中的全局作用域与 window 对象的作用域相同，因此它们的计算结果相同。
You can think of your eval("v"+e)statement as being equivalent to eval("window['v'" + e +" ]").
您可以将您的eval("v"+e)语句视为等效于eval("window['v'" + e +" ]").
回答by Marimuthu Madasamy
Both return a global variable's value. The difference is that if the global variable is undefined, you will get an error on executing eval() whereas window['variableName'] will return undefined(not an error) because accessing an undefined property is not an error but accessing an undefined variable is an error.
两者都返回一个全局变量的值。不同之处在于，如果全局变量未定义，则执行 eval() 时会出错，而 window['variableName'] 将返回 undefined（不是错误），因为访问未定义的属性不是错误，而是访问未定义的变量是一个错误。
回答by mykhal
"v"+e-> string
"v"+e-> 字符串
eval(x)-> evaluates the string x, containing javascript expression
eval(x)-> 计算字符串 x，包含 javascript 表达式
window[x]-> returns window's property with the same name, as tha value of xis. this in fact can be a global variable
window[x]-> 返回具有相同名称的窗口属性，因为它的值x是。这实际上可以是一个全局变量
therefore, when you have a global variable v1 = "foo", and e = 1, then eval("v"+e)and window["v" + e]both return "foo"
因此，当你有一个全局变量v1 = "foo", and e = 1， theneval("v"+e)和window["v" + e]都返回“foo”
