push and pop

Learn to add/remove at the end with .push and .pop.

Appending with push

To add an element at the end of an array you use .push(x). arr.push(5) places 5 at the end of arr and returns the new length. Several values can be added: arr.push(1, 2).

push modifies the array in place; it does not create a new one. For example after const nums = [1, 2]; nums.push(3);, nums becomes [1, 2, 3]. push is especially common when accumulating elements in a loop; each iteration appends a new element at the end.

Removing from the end with pop

To remove the last element of an array you use .pop(). It returns the removed element and the array length shrinks by one. In const nums = [1, 2, 3]; const last = nums.pop();, last becomes 3 and nums is left as [1, 2].

Calling pop on an empty array returns undefined; no error is thrown. push and pop together give LIFO (last in first out) stack behavior. They are handy when you want to remove the most recently added element of a list first. pop also modifies the array in place.

Exercise Append with push and print

The nums variable is set to [1, 2]. Append 3 with nums.push(3); then print nums[2] with console.log. The output on a single line must be 3.

Show example solution

const nums = [1, 2];
nums.push(3);
console.log(nums[2]);

Test yourself

Match each method to its job

push

Appends at end
pop

Removes from end
length

Element count
[0]

First element

Write the push call

const nums = [1, 2];
nums____(3);

Show answer

const nums = [1, 2];
nums.push(3);

What is the result of const a = [1, 2, 3]; a.pop();?
```
const a = [1, 2, 3];
a.pop();
```
- a = [1, 2, 3]
- a = [2, 3]
- a = [1, 2]
- a = []
Show answer

a = [1, 2] — pop removes the last element; a becomes [1, 2].

Next lesson: shift and unshift

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