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();

.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.

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