TypeScript Array findIndex() Method

The findIndex() function in TypeScript helps you find the index position of the first element in an array that meets a specified condition. If no element meets the 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 component 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: Finding the Index of the First Even Number

In this example we finds the index of the first even number in the numbers array using findIndex().

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: Finding the Index of the First Odd Number

In this example we finds the index of the first odd number in the numbers array using findIndex().

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

Output:

3