为什么 {} + {} 在 Chrome 控制台中不再是 NaN? [英] Why is {} + {} no longer NaN in Chrome console?

问题描述

我今天注意到，当您在控制台中键入 {}+{} 时，Chrome 49 不再输出 NaN.相反，它输出字符串 [object Object][object Object].

I noticed today that Chrome 49 no longer outputs NaN when you type {}+{} into the console. Instead it outputs the string [object Object][object Object].

这是为什么?语言有变化吗?

Why is this? Did the language change?

推荐答案

Chrome devtools 现在会自动将所有以 { 开头并以 } 结尾的内容包含在一对隐式的括号(见代码)，强制其评估作为表达式.这样，{} 现在创建一个空对象.如果你回顾历史(↑)，你可以看到这一点，前一行将包含在(…)中.

Chrome devtools now automatically wrap everything that begins with { and ends with } in an implicit pair of parentheses (see code), to force its evaluation as an expression. That way, {} creates an empty object now. You can see this if you go back through the history (↑), the previous line will be contained in (…).

为什么?我不知道，但是我猜它可以减少不了解块与对象字面量的新手的混淆，如果您只想评估一个表达.

Why? I don't know, but I could guess it reduces confusion for newbies that don't know of the block-vs-object-literal thing, and it's also more helpful if you just want to evaluate an expression.

事实上，这就是推理，如bug 499864.纯粹的方便.并且因为 node REPL 也有它(见代码).

And in fact that's the reasoning, as discussed in bug 499864. Pure convenience. And because node REPL had it as well (see code).

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