JavaScript includes method for String and Array with Examples

JavaScript is a powerful and versatile programming language, allowing developers to manipulate and interact with various data types, such as strings and arrays. One of the most common tasks you may encounter while working with these data types is checking whether an element or a substring is present within a given string or array. In this blog post, we will explore the includes() method in JavaScript, which provides an efficient way to accomplish this task for both strings and arrays. We will also discuss several usage examples to help you understand how to implement this method in your own projects on codedamn.

Introduction to the JavaScript includes() Method

The includes() method is a built-in JavaScript function that checks if a specific element or substring is present in an array or a string, respectively. It returns a boolean value: true if the element or substring is found and false if it is not.


For strings, the includes() method has the following syntax:

string.includes(substring, startPosition);

For arrays, the includes() method has the following syntax:

array.includes(element, fromIndex);


  • substring (for strings) / element (for arrays): The value that you want to search for within the string or array.
  • startPosition (for strings) / fromIndex (for arrays): Optional. An integer representing the index position to start the search. If not specified, the search starts from the beginning.

Using includes() with Strings

The includes() method for strings is a useful tool for searching substrings within a larger string. Let's explore some examples to better understand how this method works.

Example 1: Basic includes() usage with strings

const sentence = "Welcome to codedamn!"; const word = "codedamn"; console.log(sentence.includes(word)); // Output: true

In this example, the includes() method checks whether the word ("codedamn") is present in the sentence ("Welcome to codedamn!"). Since it is, the method returns true.

Example 2: includes() with startPosition parameter

const sentence = "Welcome to codedamn!"; const word = "Welcome"; console.log(sentence.includes(word, 1)); // Output: false

In this case, we provided a startPosition of 1, meaning the search for the word will begin at the second character of the sentence. Since "Welcome" starts at the first character, the method returns false.

Using includes() with Arrays

The includes() method for arrays is similar to its string counterpart, allowing you to search for specific elements within an array. Let's dive into some examples to see how this method works in practice.

Example 1: Basic includes() usage with arrays

const programmingLanguages = ["JavaScript", "Python", "Ruby", "Java", "C++"]; console.log(programmingLanguages.includes("Python")); // Output: true

In this example, the includes() method checks if the "Python" element is present in the programmingLanguages array. Since it is, the method returns true.

Example 2: includes() with fromIndex parameter

const programmingLanguages = ["JavaScript", "Python", "Ruby", "Java", "C++"]; console.log(programmingLanguages.includes("JavaScript", 1)); // Output: false

Here, we provided a fromIndex of 1, which means the search for the "JavaScript" element will start at the second element of the programmingLanguages array. Since "JavaScript" is the first element, the method returns false.


Q: Can I use the includes() method with case-insensitive strings?

A: The includes() method is case-sensitive. However, you can make it case-insensitive with the help of toLowerCase() or toUpperCase() methods. Convert both the main string and the substring to lower or upper case before using includes().

const sentence = "Welcome to codedamn!"; const word = "CODEDAMN"; console.log(sentence.toLowerCase().includes(word.toLowerCase())); // Output: true

Q: Can I use the includes() method with nested arrays?

A: The includes() method cannot search for elements within nested arrays directly. However, you can use nested loops or the Array.prototype.some() method in combination with includes() to achieve this.

Q: Is there an alternative to the includes() method for older browsers?

A: Older browsers might not support the includes() method. As an alternative, you can use the indexOf() method, which returns the index of the first occurrence of the specified value or -1 if the value is not found.

For more information and examples, check out the official MDN Web Docs and Array.prototype.includes() documentation.

In conclusion, the includes() method in JavaScript is a powerful and convenient tool for checking the presence of elements or substrings within strings and arrays. With the help of numerous examples provided in this blog post, you should be able to confidently use this method in your own projects on codedamn. Happy coding!

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