Move key in object of object up (swap indexes)

Question

I'm working with an object of objects. I need to keep it as an object because I'm work with an API that requires me to keep it that way (that part is not debatable).

This is an example schema of my object:

const obj = {
  1: { name: 'Initial Step 1', stepNumber: 1 },
  2: { name: 'Initial Step 2', stepNumber: 2 },
  3: { name: 'Initial Step 3', stepNumber: 3 },
}

I need to implemented a moveUp function that will take the stepNumber and obj as the first and second parameters respectively.

This moveUp function basically needs to swap one inner object with the object above it. Eg. moveUp(2, obj) should change the obj as follows:

{
  1: { name: 'Initial Step 2', stepNumber: 1 },
  2: { name: 'Initial Step 1', stepNumber: 2 },
  3: { name: 'Initial Step 3', stepNumber: 3 },
}

The stepNumber will never be equal to 1, thanks to the interface I've built.

How should I implement my moveUp function?

I basically need this:

export const moveUp = (stepNumber, obj) => {
    // I need help here
};

Thanks!

Barry if you're relying on the order here, you're going to run into an issue. Object keys don't keep a consistent order [Here](https://stackoverflow.com/questions/6959817/changing-the-order-of-the-object-keys) is some discussion on it. — Kwesi, Nov 02 '17 at 11:59
@Callam What is this snippet supposed to do/show? O.o The relevant function is empty... — Andreas, Nov 02 '17 at 12:00
@espresso_coffee The input and output I've pointed out is exactly what I want. — Barry Michael Doyle, Nov 02 '17 at 12:00
@Beau: They do as of ES2015+, but legacy operations aren't required to respect it; [details](https://stackoverflow.com/questions/30076219/does-es6-introduce-a-well-defined-order-of-enumeration-for-object-properties). — T.J. Crowder, Nov 02 '17 at 12:09

Nina Scholz · Accepted Answer · 2017-11-02T12:05:02.417

You could take a destructuring assignment and adjust stepNumber.

function moveUp(object, key) {
    [object[key], object[key - 1]] = [object[key - 1], object[key]];
    object[key].stepNumber++;
    object[key - 1].stepNumber--;
}

var object = { 1: { name: 'Initial Step 1', stepNumber: 1 }, 2: { name: 'Initial Step 2', stepNumber: 2 }, 3: { name: 'Initial Step 3', stepNumber: 3 } };

moveUp(object, 2);

console.log(object);

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

score 0 · Answer 2 · answered Nov 02 '17 at 14:22

Try this

let _ = require('lodash');
obj = {
    1: { name: 'Initial Step 1', stepNumber: 1 },
    2: { name: 'Initial Step 2', stepNumber: 2 },
    3: { name: 'Initial Step 3', stepNumber: 3 },
  }

function moveUp(sn, objToUp){
    console.log(objToUp);
    let key =  _.findKey(obj,{stepNumber: sn} );
    let keys = Object.keys(obj);
    let keyIndex = _.indexOf(keys, key);
    if(keyIndex > 0){
        let tmp = obj[keys[keyIndex-1]];
        obj[keys[keyIndex-1]] = objToUp;
        obj[keys[keyIndex]] = tmp;
    }
    console.log(obj);
}
moveUp(2, obj['2']);

Move key in object of object up (swap indexes)

2 Answers2