ECMAScript 2015:const in for循环 [英] ECMAScript 2015: const in for loops
问题描述
下面的两个(或两者/两者)代码片段中的哪一个应该在完整的ECMAScript 2015实现中工作:
for(const (a)a)(i = a; i = 1; i = a; a,a,a,a,b, )
根据我的理解,第一个例子应该工作,因为 e
被初始化为每次迭代。在第二个版本中,对于 i
也不是这样吗?
我感到困惑,因为现有的实现(Babel,IE,Firefox,Chrome,ESLint)似乎并不一致,并且具有完全实现 const
,具有两种循环变体的各种行为;我也不能在标准中找到具体的一点,所以这将是非常感激的。
-of循环工程:
for(const e of a)
ES6规范描述为:
ForDeclaration:LetOrConst ForBinding
命令式循环不起作用:
for(const i = 0; i
这是因为在执行循环体之前,声明只进行一次评估。
Which of the two (or neither/ both) code fragments below should be working in a complete ECMAScript 2015 implementation:
for (const e of a)
for (const i = 0; i < a.length; i += 1)
From my understanding, the first example should work because e
is initialized for each iteration. Shouldn't this also be the case for i
in the second version?
I'm confused because existing implementations (Babel, IE, Firefox, Chrome, ESLint) do not seem to be consistent and have a complete implementation of const
, with various behaviours of the two loop variants; I'm also not able to find a concrete point in the standard, so that would be much appreciated.
The following for-of loop works:
for (const e of a)
The ES6 specification describes this as:
ForDeclaration : LetOrConst ForBinding
The imperative for loop will not work:
for (const i = 0; i < a.length; i += 1)
This is because the declaration is only evaluated once before the loop body is executed.
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