TypeScript Array findIndex() Method

The findIndex() function, in TypeScript of array instances, helps you to find the index position of the element in an array that meets a condition, if no element meets the given condition it returns -1.

Syntax:

array.findIndex(callbackFn(value, index, array): boolean): number

Parameters:

• callbackFn: A function that is called for each element in the array. It takes three arguments:
  • element: Here we have to pass the current element that is being processed in the array.
  • index: Here we have to pass the index position of the current element which is being processed in the array.
  • array: Here we have to pass the array on which findIndex() was called upon.

Return Value:

Returns the index position of the element in an array if it meets the given condition otherwise it will return -1.

Example 1: To demonstrate finding the index position of first occurrence of even number using findIndex() method.

Javascript

const numbers: number[] = [1, 3, 8, 5, 2];
const evenIndex: number = numbers.findIndex(
    (number: number) => number % 2 === 0
);
console.log(evenIndex);

Output:

2

Example 2: To demonstrate finding the first position of first occurrence of odd number using findIndex() method.

Javascript

const numbers: number[] = [2, 4, 8, 5, 2];
const oddIndex: number = numbers.findIndex(
    (number: number) => number % 2 === 1
);
console.log(oddIndex);

Output:

3