Angular 9 How to drop a field from all arrays of an object of arrays in angular?

Question

Lets say I am having the following list which is called indexesToBeRemoved:

indexesTobeRemoved = ['auto_id', 'auto_date']

I want to loop over the following array of arrays:

allArrays = [
    {
      'auto_id': 123,
      'auto_date': '2019-02-02',
      'name': 'John Doe',
      'address': 'USA'
    },
    {
      'auto_id': 147,
      'auto_date': '2019-03-02',
      'name': 'Peter Doe',
      'address': 'USA'
    },
    {
      'auto_id': 258,
      'auto_date': '2019-04-02',
      'name': 'Hanna Doe',
      'address': 'USA'
    }
  ];

I need to loop over each array within this array to remove fields that exists in the list indexesTobeRemoved. Therefore, the array of arrays would look like the following:

allArrays = [
    {
      'name': 'John Doe',
      'address': 'USA'
    },
    {
      'name': 'Peter Doe',
      'address': 'USA'
    },
    {
      'name': 'Hanna Doe',
      'address': 'USA'
    }
  ];

I tried the following:

removeIndexes() {
    this.indexesTobeRemoved.forEach((value) => {
      console.log(value);
      Object.keys(this.allArrays).forEach((key, val) => {
        this.allArrays.splice(value, 1);
        console.log(this.allArrays[key]);
      });
    })

But on execution, the array allArray will become empty.

Here is a stackblitz.

Maheer Ali · Accepted Answer · 2020-03-26 07:27:37Z

4

You can use nested forEach() loop and delete operator

const allArrays = [ { 'auto_id': 123, 'auto_date': '2019-02-02', 'name': 'John Doe', 'address': 'USA' }, { 'auto_id': 147, 'auto_date': '2019-03-02', 'name': 'Peter Doe', 'address': 'USA' }, { 'auto_id': 258, 'auto_date': '2019-04-02', 'name': 'Hanna Doe', 'address': 'USA' } ];

let keys = ['auto_id', 'auto_date'];
allArrays.forEach(x => {
  keys.forEach(k => delete x[k])
})
console.log(allArrays)

answered Mar 26, 2020 at 7:27

Maheer Ali

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1 Comment

Maheer Ali Over a year ago

@alim1990 Accept the answer if you are satisfied with it.

Adis Alj · Accepted Answer · 2020-03-26 08:58:17Z

2

Instead of forEach please use map. Here's an explanation why:

https://gofore.com/en/why-you-should-replace-foreach/

What you were searching for was the delete operator. The JavaScript delete operator removes a property from an object; if no more references to the same property are held, it is eventually released automatically.

this.indexesTobeRemoved.map(key => {  
  this.allArrays.map(array => delete array[key]);
});

edited Mar 26, 2020 at 8:58

answered Mar 26, 2020 at 7:34

Adis Alj

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1 Comment

Adis Alj Over a year ago

this.indexesTobeRemoved.map(key => { this.allArrays.map(array => delete array[key]); });

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