JavaScript Array findIndex() method

The JavaScript array findIndex() method returns the index of first element of the given array that satisfies the provided function condition. It returns -1, if no element satisfies the condition.

Syntax

The findIndex() method is represented by the following syntax:

Parameter

callback - It represents the function that executes each element.

value - The current element of an array.

index - It is optional. The index of current element.

arr - It is optional. The array on which findIndex() method operated.

thisArg - It is optional. The value to use as this while executing callback.

Return

The index of first element of the array that satisfies the function condition.

JavaScript Array findIndex() method example

Let's see some examples of findIndex() method.

Example 1

Let's see a simple example of findIndex() method.

<script>
var arr=[5,22,19,25,34];
var result=arr.findIndex(x=>x>20);
document.writeln(result)
</script>

Test it Now

Output:

Example 2

In this example, we will find the index of prime number using findIndex() method.

<script>
function isPrime(value, index, arr) {
  var start = 2;
  while (start <= Math.sqrt(value)) {
    if (value % start++ < 1) {
      return false;
    }
  }
  return value > 1;
}
document.writeln([8, 4, 7, 22].findIndex(isPrime));
</script>

Test it Now

Output:

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