CODEWITHSUNDEEP
javascriptarraystypescript
meallhour
meallhour

Reputation: 15581

How to find first non null value in a typescript array?

I have an arr variable which looks as below:

const arr = [undefined, undefined, 'hello', 'hello', 'hi'];

I want to print out the first non-null value from within the arr array variable.

In above array, the output should be hello

I have written following logic but it is not giving the correct result:

const arr = [undefined, undefined, 'hello', 'hello', 'hi'];
const index = arr.length;

while (index-- && !arr[index]);

console.log(arr[index]);

Upvotes: 8

Views: 18627

Answers (5)

Fernando Flores
Fernando Flores

Reputation: 53

If what you mean by "non-null" is not null and not undefined then the accepted answer is incorrect because it is using strict equality check and will include null values if they were present before the first "hello".

You should use loose equality check: (only one "=")

const arr = [undefined, null, 'hello', 'hello', 'hi'];

console.log(arr.find(el => el != null)) // "el != undefined" also works

Using != null will skip any null or undefined value until it finds a different value, in this case "hello".

Upvotes: 0

Pavlo Maistruk
Pavlo Maistruk

Reputation: 326

const arr = [undefined, null, 'hello', 'hello', 'hi'];

console.log(arr.find(el => el))
// or
console.log(arr.find(el => !!el))

Upvotes: 8

Siva Kondapi Venkata
Siva Kondapi Venkata

Reputation: 11001

Start with initial index as '0'

const arr = [undefined, undefined, 'hello', 'hello', 'hi'];
let index = 0;

while (!arr[index]) index++;

console.log(index, arr[index]);

Alternatively, use findIndex

const arr = [undefined, undefined, 'hello', 'hello', 'hi'];

const index = arr.findIndex(val => val);

console.log(index, arr[index])

Upvotes: 4

Damian
Damian

Reputation: 606

None of the posted answers are incorrect, however you may hit issues if ESLint is configured to watch arrow-parens (Airbnb rules adhere to this).

If you want to adhere to best practice, utilise one of the below (very minor modification to Psidom and Pavlov's answers).

const arr = [undefined, undefined, 'Item 1', 'Item 2', 'Item 3'];

console.log(arr.find((el) => el));
console.log(arr.find((el) => el !== undefined));

Upvotes: 0

akuiper
akuiper

Reputation: 214957

Just use find:

const arr = [undefined, undefined, 'hello', 'hello', 'hi'];

console.log(arr.find(el => el !== undefined))

It returns the value of the first element in the provided array that satisfies the provided testing function.

Upvotes: 15

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