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
– nim118, Commented Nov 20, 2019 at 12:20
BTW,You have 3 arguments in your function and only 2 are given in your call. — Nico
– Nico, Commented Nov 20, 2019 at 12:20
Why do you expect the first call to move two values (4 and 5) to the front ? — Titus
– Titus, Commented Nov 20, 2019 at 12:22
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
– Titus, Commented Nov 20, 2019 at 12:30

Dipak Telangre · Accepted Answer · 2019-11-20 12:45:25Z

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, 2019 at 12:45

Dipak Telangre

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1 Comment

l00k Over a year ago

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 · Accepted Answer · 2019-11-20 12:37:59Z

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, 2019 at 12:37

answered Nov 20, 2019 at 12:22

l00k

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Comments

alireza · Accepted Answer · 2019-11-20 12:43:40Z

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, 2019 at 12:43

answered Nov 20, 2019 at 12:38

alireza

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2 Comments

l00k Over a year ago

second argument of splice method is number of element you would like to cut, not the last index

alireza Over a year ago

@l00k fixed. so it cuts and shifts last from number of values to the begning

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