JavaScript Array.prototype.shift()

The JavaScript array method .shift() will remove the first element from an array and return that value. This will also change the length of the array

Syntax

var array = [1, 2, 3, 4];
array.shift();

Description

.shift() will remove the element at index 0 of the array upon which it is called. It then returns the removed value and shifts all remaining elements down by 1 index value.

.shift() will return undefined if the array it is called on contains no elements.

Examples

Shifting the first value from an array

var array = [1, 2, 3, 4, 5];
console.log(array);
// Console will output 1, 2, 3, 4, 5

array.shift();
// If we console.log(array.shift()); the console would output 1.

console.log(array);
/* Console will output 2, 3, 4, 5 and 
the variable array now contains the set [2, 3, 4, 5] where 
each element has been moved down 1 index value. */

Source MDN