为什么我不能删除代码中的中间变量？

Question

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

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); }); 

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); }); 

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

Uncaught SyntaxError: Unexpected token ...

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).

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

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

Answer 1

Add a semicolon and it works perfectly.

 const arr = [1, 2, 3, 4]; [...arr].forEach(n => { console.log(n + 1); }); 

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

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

Which resulted in your error.