Array Search Methods
| Col 1 | Col 2 |
|---|---|
| Array indexOf() Array lastIndexOf() Array includes() | Array find() Array findIndex() Array findLast() Array findLastIndex() |
Complete JavaScript Array Reference
JavaScript Array indexOf()
The indexOf() method searches an array for an element value and returns its position.
Note: The first item has position 0, the second item has position 1, and so on.
Example
const fruits = ["Apple", "Orange", "Apple", "Mango"];
let position = fruits.indexOf("Apple") + 1;
Syntax
array.indexOf(item, start)
| Col 1 | Col 2 |
|---|---|
| item | Required. The item to search for. |
| start | Optional. Where to start the search. Negative values will start at the given position counting from the end, and search to the end. |
Array.indexOf() returns -1 if the item is not found.
If the item is present more than once, it returns the position of the first occurrence.
JavaScript Array lastIndexOf()
Array.lastIndexOf() is the same as Array.indexOf(), but returns the position of the last occurrence of the specified element.
Example
const fruits = ["Apple", "Orange", "Apple", "Mango"];
let position = fruits.lastIndexOf("Apple") + 1;
Syntax
array.lastIndexOf(item, start)
| Col 1 | Col 2 |
|---|---|
| item | Required. The item to search for |
| start | Optional. Where to start the search. Negative values will start at the given position counting from the end, and search to the beginning |
JavaScript Array includes()
ECMAScript 2016 introduced Array.includes() to arrays. This allows us to check if an element is present in an array (including NaN, unlike indexOf).
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.includes("Mango"); // is true
Syntax
array.includes(search-item)
Note: Array.includes() allows to check for NaN values. Unlike Array.indexOf().
JavaScript Array find()
The find() method returns the value of the first array element that passes a test function.
This example finds (returns the value of) the first element that is larger than 18:
Example
const numbers = [4, 9, 16, 25, 29];
let first =
numbers.find(myFunction);
function myFunction(value, index, array) {
return
value > 18;
}
Note that the function takes 3 arguments:
- The item value
- The item index
- The array itself
JavaScript Array findIndex()
The findIndex() method returns the index of the first array element that passes a test function.
This example finds the index of the first element that is larger than 18:
Example
const numbers = [4, 9, 16, 25, 29];
let first =
numbers.findIndex(myFunction);
function myFunction(value, index, array) {
return
value > 18;
}
Note that the function takes 3 arguments:
- The item value
- The item index
- The array itself
JavaScript Array findLast() Method
ES2023 added the findLast() method that will start from the end of an array and return the value of the first element that satisfies a condition.
Example
const temp = [27, 28, 30, 40, 42, 35, 30];
let high = temp.findLast(x => x > 40);
Browser Support
findLast() is an ECMAScript 2023 feature.
JavaScript 2023 is supported in all modern browsers since July 2023:
JavaScript Array findLastIndex() Method
The findLastIndex() method finds the index of the last element that satisfies a condition.
Example
const temp = [27, 28, 30, 40, 42, 35, 30];
let pos = temp.findLastIndex(x => x > 40);
Browser Support
findLastIndex() is an ECMAScript 2023 feature.
JavaScript 2023 is supported in all modern browsers since July 2023:
Note: See Also: Array Tutorial Array Constructor Array Basic Methods Array Sort Methods Array Iteration Methods Array Reference
Note: Complete JavaScript Reference For a complete reference to all JavaScript properties and methods, with full descriptions and many examples, go to: W3Schools' Full JavaScript Reference. The reference inludes all JavaScript updates from 1999 to 2025.
