JavaScript Array findIndex()

findIndex() Syntax

The syntax of the findIndex() method is:

arr.findIndex(callback(element, index, arr),thisArg)

Here, arr is an array.

findIndex() Parameters

The findIndex() method can take two parameters:

• callback - Function to execute on each element of the array. It takes in:
  • element - The current element of array.
• thisArg (optional) - Object to use as this inside callback.

findIndex() Return Value

• Returns the index of the first element in the array that satisfies the given function.
• Returns -1 if none of the elements satisfy the function.

Example 1: Using findIndex() method

Output

2

In the above example, we have used the findIndex() method to find the index of the first even number in the numbers array.

isEven() is a function that returns an even number. We have passed isEven() as a callback in the findIndex() method as- numbers.findIndex(isEven).

The method returns 2 which is the index of the first even number in numbers i.e. 8.

Example 2: findIndex() with Arrow Function

Output

1

Here we have passed an arrow function as a callback in the findIndex() method. The method returns the first index of 'Wednesday'.

Example 3: findIndex() with Object Elements

Output

2

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