The includes()
method checks if an array contains a specified element or not.
Example
// defining an array
let languages = ["JavaScript", "Java", "C"];
// checking whether the array contains 'Java'
let check = languages.includes("Java");
console.log(check);
// Output: true
includes() Syntax
The syntax of the includes()
method is:
arr.includes(valueToFind, fromIndex)
Here, arr is an array.
includes() Parameters
The includes()
method can take two parameters:
- searchValue- The value to search for.
- fromIndex (optional) - The position in the array at which to begin the search. By default, it is 0.
Note: For negative values, the search starts from array.length + fromIndex (Counting from backward). For example, -1 represents the last element.
includes() Return Value
The includes()
method returns:
true
if searchValue is found anywhere within the arrayfalse
if searchValue is not found anywhere within the array
Example 1: Using includes() method
let languages = ["JavaScript", "Java", "C", "C++"];
// checking whether the array contains 'C'
let check1 = languages.includes("C");
console.log(check1); // true
// checking whether the array contains 'Ruby'
let check2 = languages.includes("Ruby");
console.log(check2); // false
Output
true false
In the above example, we have used the includes()
method to check whether the languages array contains elements 'C'
and 'Ruby'
.
languages.includes("C")
returns true
since the array contains 'C'
and languages.includes("Ruby")
returns false
since the array does not contain 'Ruby'
.
Example 2: includes() for Case-Sensitive Search
The includes()
method is case sensitive. For example:
let languages = ["JavaScript", "Java", "C", "Python"];
// checking whether the array contains 'Python'
let check1 = languages.includes("Python");
console.log(check1); // true
// checking whether the array contains 'python'
let check2 = languages.includes("python");
console.log(check2); // false
Output
true false
Here the includes()
method returns true
for searchValue- 'Python'
and false
for 'python'
.
This is because the method is case sensitive and it treats 'Python'
and 'python'
as two different strings.
Example 3: includes() with two Parameters
let languages = ["JavaScript", "Java", "C", "Python"];
// second argument specifies position to start the search
let check1 = languages.includes("Java", 2);
console.log(check1); // false
// the search starts from third last element
let check2 = languages.includes("Java", -3);
console.log(check2); // true
Output
false true
In the above example, we have passed two argument values in the include()
method.
languages.includes("Java", 2)
returns false
since the method doesn't find 'Java'
from second index of the array.
In languages.includes("Java", -3)
, the method starts searching 'Java'
from the third last element because of the negative argument -3.
Recommended Reading: JavaScript Array indexOf()