Consider the following code snippet :

var a = []; 
a.unshift(1); 
a.unshift(22);
a.shift(); 
a.unshift(3,[4,5]); 
a.shift(); 
a.shift();
a.shift();

The final output for the shift() is

The unshift() and shift() methods behave much like push() and pop(), except that they insert and remove elements from the beginning of an array rather than from the end. unshift() adds an element or elements to the beginning of the array, shifts the existing array elements up to higher indexes to make room, and returns the new length of the array. shift() removes and returns the first element of the array, shifting all subsequent elements down one place to occupy the newly vacant space at the start of the array.