Shifting array element by indexes

Question

I have been trying to solve this program. I have a list of objects that look like this. Adding elements to an array based on their index position.

let A = {index: 0} 
let B = {index: 0} 
let C = { index: 2} 
let D = {index: 2} 
let E = { index: 1}

So if A get pushed inside the array it takes over an array index position 0. However, when B get pushed in the array, it will take over an index position. [B, A], and so on. It is sort of like first go in, first come out, except get shifted to the left. However, I want to do something like this. [B, A, C], I want to add D to index position of C. [B, A, D, C]. A is at index position 1. I want to insert E to index 1. [B, E, A, D, C]

You can probably use Array.concat(). Also please include the code you currently have when posting a question. — HollyLeaves
– HollyLeaves, Commented Apr 11, 2018 at 18:38

Jonas Wilms · Accepted Answer · 2018-04-11 18:38:31Z

3

  function insert(array, el) {
     let pos = 0;
     while(array[pos].index < el.index) pos++;
     array.splice(pos, 0, el);
  }

Just do insertion sort and use splice to add the element.

answered Apr 11, 2018 at 18:38

Jonas Wilms

139k20 gold badges164 silver badges164 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Jonas Wilms Over a year ago

@nina oh really? I think its really clear what the OP wants :)

HollyLeaves Over a year ago

Why do we need the while loop if we already know the position to insert at. Like doesn't OP mean to insert D at pos = 2 or did I misunderstand?

Jonas Wilms Over a year ago

@hollyleaves actually that depends on how you interpret the question.

HollyLeaves Over a year ago

You're right, I see you actually tried to preserve the index order

Nina Scholz · Accepted Answer · 2018-04-11 18:46:15Z

2

You could simply splice the array for adding an object at the wanted index.

var a = { index: 0, value: 'a' },
    b = { index: 0, value: 'b' },
    c = { index: 2, value: 'c' },
    d = { index: 2, value: 'd' },
    e = { index: 1, value: 'e' },
    array = [];

function add(array, object) {
    array.splice(object.index, 0, object);
}

add(array, a);
add(array, b);
add(array, c);
add(array, d);
add(array, e);

console.log(array);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Apr 11, 2018 at 18:46

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

3 Comments

Jonas Wilms Over a year ago

Oh right, removing thanks in advance from the question made it on-topic?! Thats interesting ...

Jonas Wilms Over a year ago

No, but you complained about my answer, and now surprisingly you add an answer eventhough the question hasnt really changed...

Nina Scholz Over a year ago

right, after reading you answer and checking the wanted outcoume, i thought a concise answer would help.

Ele · Accepted Answer · 2018-04-11 19:23:04Z

0

You can use the function splice and check for the index attribute to insert at a specific position.

If the index attribute doesn't exist, push the object at the end.

var decorate = (arr) => {
  arr.insertByIndex = (...objs) => {
    objs.forEach(obj => {
      if (!isNaN(obj.index)) arr.splice(obj.index, 0, obj);
      else arr.push(obj);
    });
  }
  
  return arr;
};

let A = {index: 0, desc: 'A'};
let B = {index: 0, desc: 'B'};
let C = {index: 2, desc: 'C'};
let D = {index: 2, desc: 'D'};
let E = {index: 1, desc: 'E'};

var array = decorate([]);
array.insertByIndex(D, A, C, B, E);

console.log(array);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Apr 11, 2018 at 19:23

answered Apr 11, 2018 at 18:48

Ele

33.8k7 gold badges43 silver badges80 bronze badges

Collectives™ on Stack Overflow

Shifting array element by indexes

3 Answers 3

4 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related