为什么我不能在代码中删除中间变量? [英] Why can't I remove the intermediate variable in my code?

问题描述

我目前正在使用传播语法，但遇到了意外问题.

I'm currently working with the spread syntax and ran into an unexpected issue.

下面的代码段可以正常工作，并且不会引发任何错误:

The below snippet works (as expected), and doesn't throw any errors:

const arr = [1, 2, 3, 4] // create array of numbers

const copy = [...arr] // make a shallow copy of the array
copy.forEach(n => { // loop through array
  console.log(n + 1);
});

但是，如果我删除中间变量copy，我的代码似乎会抛出错误:

However, if I remove the intermediate variable copy, my code seems to throw an error:

const arr = [1, 2, 3, 4] // create array of numbers

[...arr].forEach(n => { // loop through array
  console.log(n + 1);
});

如您所见，以上代码片段引发错误:

As you can see, the above code snippet throws an error:

未捕获到的SyntaxError:意外令牌...

Uncaught SyntaxError: Unexpected token ...

第一个代码段没有. 为什么会这样?据我了解，我应该能够将copy替换为包含但没有问题的文字数组(就像我在第二个片段中所做的那样).

Whereas the first snippet does not. Why is this happening? To my understanding I should be able to replace copy with literal array it contains and have no issues (as I have done in the second snippet).

我希望第二个片段的行为与第一个片段相同，并且不会引发任何错误.

I expect the second snippet to behave as the first snippet, and not throw any errors.

注意:我知道[...arr]在这种情况下似乎是多余的，我只是用它来演示我的问题.

Note: I'm aware that [...arr] seems redundant in this case, I've simply used this to demonstrate my problem.

推荐答案

添加分号，效果很好.

Add a semicolon and it works perfectly.

const arr = [1, 2, 3, 4];

[...arr].forEach(n => {
  console.log(n + 1);
});

正在评估的代码没有换行符-像这样:

The code was being evaluated without the newline - like this:

const arr = [1, 2, 3, 4][...arr]

哪个导致了您的错误.

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