Why doesn't array.splice() work when the array has only 1 element?

Question

Is this intended behavior? I would expect an empty array to be returned here.

JavaScript

let arr = [1];
console.log(arr.splice(0, 1))

Console

1

Illfated

It returns 1, which is a proper result. – Incised

But if I am starting at index 0, and removing 1 item then why would it not return an empty array? – Illfated

Because splice() returns the value which was 'spliced/cut/removed' from the original array. Try console.log(arr) and you will see that it's empty. – Incised

Answer 1

Because it returns what was removed, which is [1] in your case. arr will be empty after the call.

See example:

let arr = [1];
arr.splice(0, 1);
console.log(arr);

Subeditor

ohh I thought it returned the modified array – Illfated

Answer 2

Array.prototype.splice() returns an array of the deleted elements.

Your are logging the returned value of the operation not the current state of the array.

Nicosia

Answer 3

The splice() method changes the contents of an array by removing existing elements and/or adding new elements. Reference

The syntax of this method is:

array.splice(start)
array.splice(start, deleteCount)
array.splice(start, deleteCount, item1, item2, ...)

You are using the second syntax and passing 0 as start and 1 as deleteCount that means you would like to start at 0th index and delete 1 item (not 1 as value in array).

This method returns an array containing the deleted elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.

So, in this case the result is [1] i.e. an array with value of 1 that is the item you just deleted.

Ahmednagar

Answer 4

I ran into this question when I was trying to achieve a function in mini-program. A solution is to check the array's length before using the function splice. For example:

if(imgList.length > 1){
    imgList.splice(index, 1);
else{
    imgList = []
}

You can try to solve it like that.

Vitebsk