shift array from index javascript code example

Example 1: array shift javascript

//The shift() method removes the first element from an array 
//and returns that removed element. 
//This method changes the length of the array.

const array1 = [1, 2, 3];
const firstElement = array1.shift();
console.log(array1);
// expected output: Array [2, 3]
console.log(firstElement);
// expected output: 1

Example 2: javascript move item in array to another index

function moveArrayItemToNewIndex(arr, old_index, new_index) {
    if (new_index >= arr.length) {
        var k = new_index - arr.length + 1;
        while (k--) {
            arr.push(undefined);
        }
    }
    arr.splice(new_index, 0, arr.splice(old_index, 1)[0]);
    return arr; 
};

//move index 1(b) to index 2(c)
console.log(moveArrayItemToNewIndex(["a","b","c","d"], 1, 2)); // returns ["a", "c", "b", "d"]