为什么`{} + []`返回的结果不同于Java中的`a = {} + []`? [英] Why does `{} + []` return a different result from `a = {} + []` in Javascript?

问题描述

在(至少)Firefox Web Console和JSBin中，我得到了

In (at least) Firefox Web Console and JSBin, I get

> {} + []
0
> a = {} + []
"[object Object]"

在两种情况下，

Node.js返回"[object Object]" .根据规范，哪种行为是正确的?如果是第一个，为什么?

Node.js returns "[object Object]" in both cases. Which behavior is correct according to the spec? If the first, why?

推荐答案

在浏览器控制台上，当它前面没有 = (或其他更改其上下文的代码)时， {} 被视为 block ，而不是对象文字.

On the browser console, when it isn't preceded by a = (or some other code that changes its context), {} is treated as a block, not an object literal.

由于该块为空，因此不执行任何操作，而保留 + [] .

Since the block is empty it does nothing, leaving + [].

一元加号运算符将数组转换为数字，即 0 .

The unary plus operator converts the array to a number, which is 0.

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