Efficient way to delete key of object in nested arrays

Question

My data is structured like this:

obj = {
    _id: "sjkd9skj",
    data: {
      dektop: [
                { 
                   x: 2,
                   y: 3,
                   t: { key: 'aabbcc'}
                }, 
                ... 
              ],
      mobile: [
                { 
                   x: 4,
                   y: 3,
                   t: { key: 'ffff'}
                }, 
                ... 
              ],
      print: [
                { 
                   x: 7,
                   y: 5,
                   t: { key: 'ppp'}
                }, 
                ... 
              ]
    }
}

In data, I need to remove all t keys from all array elements for all modes (desktop,mobile,print).

What would be the most efficient way to do this? These mode arrays can get quite large.

I have tried it like this:

obj.data.mobile.forEach((item)=>{
    delete item.t;
});
obj.data.desktop.forEach((item)=>{
    delete item.t;
});
obj.data.print.forEach((item)=>{
    delete item.t;
});

Which does actually not manipulate the obj in this case, so it did not work. Any better suggestions?

Thanks @Kinduser I'm seeing this issue in my app as I'm passing states to be manipulated in redux. It must be related then to a immutability issue. This obj was returned from graphql call. Seems like I would have to deebug deeper. or copy said object, which I don't want to do. — Gerrie van Wyk
– Gerrie van Wyk, Commented Jul 25, 2017 at 11:43
Sorry, was not sure this is the issue. I though immutability is only valid for pure types not nested object. Guess I have some reading to do... — Gerrie van Wyk
– Gerrie van Wyk, Commented Jul 25, 2017 at 11:47

kind user · Accepted Answer · 2017-07-25 14:38:26Z

1

I hope it's not blowing up open door, but you can try reduce aproach. Immutability requirement is fulfilled.

let obj = {_id:"sjkd9skj",data:{dektop:[{x:2,y:3,t:{key:'aabbcc'}},{x:2,y:3,t:{key:'aabbcc'}}],mobile:[{x:4,y:3,t:{key:'ffff'}},],print:[{x:7,y:5,t:{key:'ppp'}},]}};

const { _id } = obj;

let newObj = Object.keys(obj.data).reduce((s, a) => {
  obj.data[a].forEach((_, i) => {
    if (obj.data[a][i].t) {
      delete obj.data[a][i].t;
    }
  })
  s.data[a] = obj.data[a];
  return s;
}, { _id, data: {} });

console.log(newObj);

edited Jul 25, 2017 at 14:38

answered Jul 25, 2017 at 11:43

kind user

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2 Comments

Pedro Corso Over a year ago

Works only if there's a single element on each array. Test: jsfiddle.net/rpd9pzmt

kind user Over a year ago

@PedroCorso Ah, yeah, indeed. Missed the three dots after single arrays :) Fixed!

Pedro Corso · Accepted Answer · 2017-07-25 14:47:31Z

1

Not sure if I'm being helpful here, but copying the data (without t property) to a new object seems to be faster than the delete method: https://jsperf.com/removing-object-props

EDIT: I've edited the test cases to fix Kind user's code. Copying is still faster.

edited Jul 25, 2017 at 14:47

answered Jul 25, 2017 at 12:35

Pedro Corso

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5 Comments

Gerrie van Wyk Over a year ago

Very interesting to see that delete is so slow.

Pedro Corso Over a year ago

The tests are now corrected. Reduce method is actually almost as slow as deleting.

Gerrie van Wyk Over a year ago

Thanks Pedro. This is useful!!

keithpjolley Over a year ago

The jsperf.com link is 404.

Pedro Corso Over a year ago

@keithpjolley Not sure what happened. I tried to check the "My tests" page but it is giving me 404 too. It seems that I'm not the only one.

Hassan Imam · Accepted Answer · 2017-07-25 11:40:15Z

0

You can use array#forEach to delete t key.

var obj = {
    _id: "sjkd9skj",
    data: {
      dektop: [
                { 
                   x: 2,
                   y: 3,
                   t: { key: 'aabbcc'}
                }
              ],
      mobile: [
                { 
                   x: 4,
                   y: 3,
                   t: { key: 'ffff'}
                } 
              ],
      print: [
                { 
                   x: 7,
                   y: 5,
                   t: { key: 'ppp'}
                }
              ]
    }
}

Object.keys(obj.data).forEach(o => {
  obj.data[o].forEach(p => delete p['t'])
});
console.log(obj);

answered Jul 25, 2017 at 11:40

Hassan Imam

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Comments

ewwink · Accepted Answer · 2017-07-25 12:03:59Z

0

not manipulated because you're deleting output object not object from object

obj = {
  _id: "sjkd9skj",
  data: {
    dektop: [{
        x: 2,
        y: 3,
        t: {
          key: 'aabbcc'
        }
      },
    ],
    mobile: [{
        x: 4,
        y: 3,
        t: {
          key: 'ffff'
        }
      },
    ],
    print: [{
        x: 7,
        y: 5,
        t: {
          key: 'ppp'
        }
      },
    ]
  }
}

Object.keys(obj.data).forEach((item) => {
 delete obj.data[item][0].t;
});

console.log(obj.data)

answered Jul 25, 2017 at 12:03

ewwink

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