JavaScript Array findIndex() Method
Example
Get the index of the first element in the array that has a value of 18 or more:
var ages = [3, 10, 18, 20];
function checkAdult(age) {
return age >= 18;
}
function myFunction() {
document.getElementById("demo").innerHTML = ages.findIndex(checkAdult);
}
The result will be:
2
Try it Yourself »
More "Try it Yourself" examples below.
Definition and Usage
The findIndex() method returns the index of the first element in an array that pass a test (provided as a function).
The findIndex() method executes the function once for each element present in the array:
- If it finds an array element where the function returns a true value, findIndex() returns the index of that array element (and does not check the remaining values)
- Otherwise it returns undefined
Note: findIndex() does not execute the function for array elements without values.
Note: findIndex() does not change the original array.
Browser Support
The numbers in the table specify the first browser version that fully supports the method.
| Method | |||||
|---|---|---|---|---|---|
| findIndex() | 45.0 | 12.0 | 25.0 | 7.1 | 32.0 |
Syntax
array.findIndex(function(currentValue,index,arr),thisValue)
Parameter Values
| Parameter | Description | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| function(currentValue, index,arr) | Required. A function to be run for each element in the array. Function arguments:
|
||||||||
| thisValue | Optional. A value to be passed to the function to be used as
its "this" value. If this parameter is empty, the value "undefined" will be passed as its "this" value |
Technical Details
| Return Value: | Returns the array element index if any of the elements in the array pass the test, otherwise it returns undefined |
|---|---|
| JavaScript Version: | ECMAScript 6 |
More Examples
Example
Get the index of the first element in the array that has a value above a specific number:
<p>Minimum age: <input type="number" id="ageToCheck" value="18"></p>
<button onclick="myFunction()">Try it</button>
<p>Any ages above:
<span id="demo"></span></p>
<script>
var ages = [4, 12, 16, 20];
function checkAdult(age) {
return age >=
document.getElementById("ageToCheck").value;
}
function
myFunction() {
document.getElementById("demo").innerHTML = ages.findIndex(checkAdult);
}
</script>
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JavaScript Array Reference
