JavaScript Boolean Object JavaScript Array Object

JavaScript array findIndex() method

findIndex()The method returns the index of the first element in the array that satisfies the provided test function.

findIndex()The method calls the function once for each element in the array:

When the elements in the array return true when tested, findIndex() returns the index position of the element that meets the conditions, and the subsequent values will not call the execution function
If there is no element that meets the conditions, it will return -1

Note: The findIndex() method does not change the original array.

Note: The function will not be executed for an empty array for findIndex().

Syntax:

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

Example

var num = [1,　30,　39,　29,　10,　13];
var val = num.findIndex(myFunc);
function myFunc(element) {
return element >=　18;
}

Test and See‹/›

See alsofind()A method that returns the value of the element found in the array instead of its index.

Browser compatibility

The numbers in the table specify the first browser version that fully supports the findIndex() method:

Method
findIndex()	45	25	32	8	12

Parameter value

Parameter	Description
callback	A function that runs for each element in the array. Function parameters: element(Required)-The current element being processed in the array index(Optional)-The index of the current element being processed in the array arr(Optional)-Optional. The array object to which the current element belongs
thisArg	Optional. The value passed to the function is generally the "this" value. If this parameter is empty, "undefined" will be passed to the "this" value

Technical details

Return value:	If the element passes the test, it is in the array.Index; otherwise it is-1
JavaScript Version:	ECMAScript 6

More Examples

The following example returns the index of an element in the array that is a prime number; if there is no prime number, it returns-1:

Example

var array1　= [1,　15,　17,　24,　29,　10,　13];
function isPrime(element) {
　　var start =　2;
　　while (start <= Math.sqrt(element)) {
　　　　　if (element % start <　1) {
　　　　　　　　　return false;
　　　　　} else {
　　　　　　　　　start++;
　　　　　}
　　}
　　return element >　1;
}
function myFunc1() {
　　　document.getElementById("result").innerHTML = array1.findIndex(isPrime);
}

Test and See‹/›

　JavaScript Array Object