How to shift values inside array in javascript

Question

I have an array with elements. for ex - let data = [ 1, 2, 3, 4, 5 ];

Now if I pass 2 in function as a parameter, then the last two value will move to first in the array.

 let data = [1, 2, 3, 4, 5];
 functionname(data, 2);
 //Expected output - 4,5,1,2,3

Now if I pass 3 in function as a parameter, then the last three value will move to first in the array.

  let data = [ 1, 2, 3, 4, 5 ];
    functionname(data, 3);
    //Expected output - 3,4,5,1,2

@FelixKling Problem is , current code is not giving expected output. — nim118, Nov 20 '19 at 12:20
BTW,You have 3 arguments in your function and only 2 are given in your call. — Nico, Nov 20 '19 at 12:20
No i just tried to get my expected output bt i was unable to solve — Sai, Nov 20 '19 at 12:22
Why do you expect the first call to move two values (`4` and `5`) to the front ? — Titus, Nov 20 '19 at 12:22
Please forgot my code just consider my expected output and help me to achieve this. — Sai, Nov 20 '19 at 12:27
Even with the updated requirements the expected output for the second call is wrong. Moving the last 3 values of `4,5,1,2,3` to the front will result in `1,2,3,4,5`. — Titus, Nov 20 '19 at 12:30
Last time I udpated answer.. next time better precise you requirement — l00k, Nov 20 '19 at 12:37

score 2 · Answer 1 · answered Nov 20 '19 at 12:45

2

Immutable

function insertAndShift(arr, from) {
    return [...arr.slice(-from), ...arr.slice(0, arr.length - from)];
}
insertAndShift([1,2,3,4,5], 2) // [4, 5, 1, 2, 3]
insertAndShift([1,2,3,4,5], 3); // [3, 4, 5, 1, 2]

answered Nov 20 '19 at 12:45

Dipak Telangre

1,792
4
19
46

Nice. However on defense of my answer - if you check history of this question you will find out it looked like mutability were required. – l00k Nov 20 '19 at 13:51

l00k · Accepted Answer · 2019-11-20T12:37:59.067

0

function insertAndShift(data, len) 
{
    let cutOut = data.splice(-len);         // cut <len> elements from the end
    data.splice(0, 0, ...cutOut);           // insert it at index 0
}
    
let data = [1,2,3,4,5];
insertAndShift(data, 2);
console.log(data);

data = [1,2,3,4,5];
insertAndShift(data, 3);
console.log(data);

edited Nov 20 '19 at 12:37

answered Nov 20 '19 at 12:22

l00k

1,525
1
19
29

alireza · Answer 3 · 2019-11-20T12:43:40.327

0

Here you are

function insertAndShift(arr, from) {
        let cutOut = arr.splice(arr.length - from, arr.length); 
        arr.splice(0, 0, ...cutOut);            
    }
    
let data = [ 1, 2, 3, 4, 5];

insertAndShift(data, 2)
console.log(data)

data = [ 1, 2, 3, 4, 5];
insertAndShift(data, 3)
console.log(data)

edited Nov 20 '19 at 12:43

answered Nov 20 '19 at 12:38

alireza

518
5
15

second argument of splice method is number of element you would like to cut, not the last index – l00k Nov 20 '19 at 12:39
@l00k fixed. so it cuts and shifts last `from` number of values to the begning – alireza Nov 20 '19 at 12:45

How to shift values inside array in javascript

3 Answers3