Create array of object with condition

Question

I am creating array of object. I want to add object based on condition. But, It add false instead of not adding object in array.

I tried:

const flag = false;
const list = [
      { key: 'abc', label: 'abcd' },
      flag && { key: 'bbb', label: 'abcd' },
      { key: 'ccc', label: 'abcd' },
      flag && { key: 'ddd', label: 'abcd' },
      { key: 'eee', label: 'abcd' },
   ];
   
console.log(list);

You can check output there are false in array.

flag && { key: 'bbb', label: 'abcd' }, always returns a value. And the value is the result of the expression. If you don't want to add something, then your best bet is a simple if(flag) list.push({ key: 'bbb', label: 'abcd' });. You can also do it as part of the array initialisation but it's too much of a hassle. — VLAZ
– VLAZ, Commented Nov 12, 2020 at 11:11
@VLAZ Yeah, but that add object to last. I don't want to change order. — ketan
– ketan, Commented Nov 12, 2020 at 11:19
Yes, I was just trying to not too much code in the comment, as it's hard to read. I thought it would be clear that you need to change how the array is populated to list.push({ key: 'abc', label: 'abcd' }); if (flag) list.push({ key: 'bbb', label: 'abcd' }); list.push({ key: 'ccc', label: 'abcd' }); if (flag) list.push({ key: 'ddd', label: 'abcd' }); list.push({ key: 'eee', label: 'abcd' }) — VLAZ
– VLAZ, Commented Nov 12, 2020 at 11:24

Krzysztof Krzeszewski · Accepted Answer · 2020-11-12 11:22:19Z

2

Assuming that all elements that are to be kept in the array do not have falsey values, you could simply filter them based on the value afterwards like so:

const flag = false;
const list = [
  { key: 'abc', label: 'abcd' },
  flag && { key: 'bbb', label: 'abcd' },
  { key: 'ccc', label: 'abcd' },
  flag && { key: 'ddd', label: 'abcd' },
  { key: 'eee', label: 'abcd' }
].filter(Boolean);
   
console.log("list:", list);

const flag2 = true;
const list2 = [
  { key: 'abc', label: 'abcd' },
  flag2 && { key: 'bbb', label: 'abcd' },
  { key: 'ccc', label: 'abcd' },
  flag2 && { key: 'ddd', label: 'abcd' },
  { key: 'eee', label: 'abcd' }
].filter(Boolean);

console.log("list2:", list2);

edited Nov 12, 2020 at 11:22

answered Nov 12, 2020 at 11:10

Krzysztof Krzeszewski

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1 Comment

Evan Trimboli Over a year ago

I thought the question was tagged as typescript. This approach is more legible for sure.

Evan Trimboli · Accepted Answer · 2020-11-12 11:11:36Z

2

To do it all in a single statement, you can use the spread operator:

const list = [
  { key: 'abc', label: 'abcd' },
  ...(flag ? [{ key: 'bbb', label: 'abcd' }] : []),
  { key: 'ccc', label: 'abcd' },
  ...(flag ? [{ key: 'ddd', label: 'abcd' }] : []),
  { key: 'eee', label: 'abcd' },
];

It's pretty ugly though.

answered Nov 12, 2020 at 11:11

Evan Trimboli

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