I have an array ["a","b","c","d","e"].
I want to move element index 1,2 to move one step up/down in the order so that new array would be ["b","c","d","e","a"].
If it is single element only, I can do that, but I could not figure out, how to do that in JavaScript.
The number of index elements to be moved can be any, e.g. it can be 1 element only or more than 2.
Please help me.
A little function if you want to move the indices by an arbitrary offset.
//returns a new array with the items shifted
function move(arr, offset=0){
//positive offsets move right
const pivot = (offset < 0? 0: arr.length) - offset % arr.length;
//positive offsets move left
//const pivot = (offset < 0? arr.length: 0) + offset % arr.length;
return arr.slice(pivot).concat(arr.slice(0, pivot));
}
let arr = ["a","b","c","d","e","f"];
for(let i=-5; i<10; ++i){
console.log("shifted by %i %s", i, move(arr, i));
}.as-console-wrapper{top:0;max-height:100%!important}You could shift and push the element.
const
down = array => array.push(array.shift()),
up = array => array.unshift(array.pop());
var array = ["a", "b", "c", "d", "e"];
up(array);
console.log(array);
down(array);
console.log(array);
Use push and splice ()
var noOfItems = 2;
arr.push.apply( arr, arr.splice( 0, noOfItems ) );
Demo
var arr = ["a","b","c","d","e"]
var noOfItems = 2;
arr.push.apply( arr, arr.splice( 0, noOfItems ) );
console.log(arr);Or if you want to do the reverse, then use unshift
arr.unshift( arr.pop() )
And for multiple elements
arr.unshift.apply( arr, arr.splice(-2) )
Demo
var arr = ["a","b","c","d","e"]
var noOfItems = 2;
arr.unshift.apply( arr, arr.splice( -noOfItems ) )
console.log(arr);
You can use array.prototype.unshift, array.prototype.push and array.prototype.splice:
var arr = ["a","b","c","d","e"];
function rotateRight(arr, nb) {
var rightPart = arr.splice(arr.length - nb, arr.length);
arr.unshift(...rightPart);
}
function rotateLeft(arr, nb) {
var leftPart = arr.splice(0, nb);
arr.push(...leftPart);
}
rotateRight(arr, 3);
console.log(arr);
rotateLeft(arr, 3);
console.log(arr);