使用数组解构分配调用哪个 function？

Question

 let [x, y] = ["Ele", "Stack"].reduce((a, s) => { ax = s; ay = s; return a; }, { x: {}, y: {}});

The code snippet above throws an error because is trying to make an array destructuring assignment over an object (key:value).

I have a lack of knowledge

Which function is being called using an array destructuring assignment?

Answer 1

I think you are getting that type error because array destructuring implicitly calls Array[Symbol.iterator] , which is undefined since you're actually returning an object, not an array, from reduce() . The fix is to replace it with Object destructuring

 let {x, y} = ["Ele", "Stack"].reduce((a, s) => { ax = s; ay = s; return a; }, { x: {}, y: {}}); console.log({ x, y })

Answer 2

The array destructuring works like it's taking the index of the array and put it into the variables you assigned.

For example, say the array is-

const arr = [1, 2, 3, 4, 5];

Now you want to destructure the array elements into variables.

const [a, b] = arr;

This will put the value off arr[0] into a and arr[1] into b . This way you can assign as many as you want.

If you want to put two indexes into two variables and rest of the elements into another array you do it by using spreading operator like this-

const [a, b, ...rest] = arr;

Here, a takes the value of arr[0] and b takes the element of arr[1] and rest takes the rest of the elements into rest array. So the rest array would be-

[3, 4, 5]

I hope this will help you.