includes()

In JavaScript, the includes() method is a simple and efficient way to check if an array contains a specific value. This method returns a boolean value: true if the array contains the specified element, and false otherwise.

The includes() method is particularly useful when you need to quickly verify the presence of an element in an array without needing to know its exact position. Let’s start with an example of how to use the includes() method

let fruits = ["apple", "banana", "orange", "mango"];
console.log(fruits.includes("banana")); // true
console.log(fruits.includes("grape"));  // false

In this example, we have an array of fruits. We use the includes() method to check if banana is in the array. It returns true because banana is indeed present. We then check for grape, which returns false because it’s not in the array.

The includes() method is case-sensitive when dealing with strings. This means that Banana with a capital B and banana with all lowercase letters are considered different values. Here’s an example that illustrates this

let fruits = ["apple", "banana", "orange"];
console.log(fruits.includes("banana")); // true
console.log(fruits.includes("Banana")); // false

In this case, banana (all in lowercase) is found in the array, but Banana (with the first letter capitalized) is not, so the second includes() call returns false.

The includes() method can also accept an optional second parameter that specifies the position in the array to start the search. This is useful if you want to check for an element’s presence in a specific part of the array. Here’s how you can use this feature

let numbers = [10, 20, 30, 40, 50, 30, 60];
console.log(numbers.includes(30, 3)); // true
console.log(numbers.includes(30, 4)); // true

For the first console.log, we are looking for the number 30 starting at index 3. In this case, there is a number 30 that appears after index 3, so the includes() method returns true.

The same is true for the second console.log. We are looking for the number 30 starting at index 4. Since the number 30 does appear after that index, then it will return true.

It’s worth noting that includes() uses the strict equality comparison (===), which means it can distinguish between different types. For example

let mixedArray = [1, "2", 3, "4", 5];
console.log(mixedArray.includes(2));  // false
console.log(mixedArray.includes("2")); // true

In this case, the number 2 and the string "2" are considered different data types. So, the first console.log will return false, while the second console.log will return true.

The includes() method is a powerful tool for checking the presence of elements in arrays. It’s simple to use, efficient, and can save you from writing more complex loops or conditions to search through arrays. Whether you’re working with strings, numbers, or mixed data types, includes() provides a straightforward way to verify if a value exists in your array.