2

I know that array is some kind of an object, but it also has numeric indexes. And arr.length is a property, which returns not the number of elements in the array, but the last index+1. We can remove the last element using decrement of length or function pop(). And the question is: What's the difference between these methods?

jpyams
  • 3,455
  • 5
  • 34
  • 59
GigaGeek
  • 81
  • 7
  • you get the item with `pop`...? what is the changing of length for? – Nina Scholz Jul 06 '19 at 16:57
  • 1
    [Is it an antipattern to set an array length in JavaScript?](https://stackoverflow.com/questions/31547315) and [Javascript array length modification implications](https://stackoverflow.com/questions/43712345) – adiga Jul 06 '19 at 17:00

2 Answers2

7

Some differences:

  • pop returns the value of the entry that you're removing, assigning to length doesn't.

  • pop is a method call; assigning to length is an assignment operation.

  • pop on an array whose length is 0 returns undefined and doesn't change the array. array.length -= 1 on an array with a length of 0 causes an error.

T.J. Crowder
  • 959,406
  • 173
  • 1,780
  • 1,769
3

.pop() also returns the last element (which is often wanted):

   const last = array.pop();
  // vs
  const last = array[array.length - 1];
  array.length -= 1;

Now you can decide yourself which one of the above is more readable ...

Jonas Wilms
  • 120,546
  • 16
  • 121
  • 140