JavaScript Eng Tutorial-75: String Methods | Startswith, Endswith, Includes
Welcome to JavaScript Tutorial-75: String Methods | Startswith, Endswith, Includes! In this comprehensive tutorial, we'll dive into the fascinating world of JavaScript string methods. Strings are essential in any programming language, and JavaScript provides us with various built-in methods to manipulate and search for substrings within a string. In this tutorial, we'll focus on three important string methods: startsWith(), endsWith(), and includes(). These methods are widely used in web development and have the potential to streamline your code and make your applications more efficient. So, let's get started and explore each of these string methods in detail.
JavaScript Tutorial-75: String Methods | Startswith
What is startsWith()?
startsWith() is a built-in JavaScript method that checks whether a string starts with a specified substring. It returns a boolean value, true if the string starts with the provided substring, and false otherwise.
How to use startsWith()?
To use the startsWith() method, you can call it on any string object and pass the substring you want to check as an argument. Let's look at an example:
const str = "Hello, world!";
const startsWithHello = str.startsWith("Hello");
console.log(startsWithHello); // Output: trueIn this example, the startsWith() method checks whether the string str starts with "Hello." Since it does, the method returns true.
Practical Use Case: URL Validation
One practical use case for startsWith() is in URL validation. You can use it to ensure that a given URL starts with the expected protocol, such as "https://" or "http://". Let's see how you can do that:
function isValidURL(url) {
return url.startsWith("https://") || url.startsWith("http://");
}
const websiteURL = "https://www.example.com";
const isValid = isValidURL(websiteURL);
console.log(isValid); // Output: trueHere, the isValidURL() function checks whether the websiteURL starts with either "https://" or "http://". If it does, it returns true, indicating a valid URL.
JavaScript Tutorial-75: String Methods | Endswith
What is endsWith()?
endsWith() is another powerful string method in JavaScript that checks whether a string ends with a specified substring. Like startsWith(), it returns a boolean value, true if the string ends with the provided substring, and false otherwise.
How to use endsWith()?
Similar to startsWith(), you can use the endsWith() method by calling it on a string object and passing the desired substring as an argument. Here's an example:
const str = "Hello, world!";
const endsWithWorld = str.endsWith("world!");
console.log(endsWithWorld); // Output: trueIn this case, the endsWith() method checks whether the string str ends with "world!". As it does, the method returns true.
Practical Use Case: File Extension Validation
Consider a scenario where you want to validate whether a given filename has a specific file extension, such as ".txt" or ".pdf". The endsWith() method can come in handy:
function isValidFileExtension(filename, extension) {
return filename.endsWith(extension);
}
const fileName = "report.txt";
const validExtension = ".txt";
const isValid = isValidFileExtension(fileName, validExtension);
console.log(isValid); // Output: trueHere, the isValidFileExtension() function checks whether the fileName ends with the validExtension. If it does, it returns true, indicating a valid file extension.
JavaScript Tutorial-75: String Methods | Includes
What is includes()?
The includes() method is yet another valuable addition to JavaScript's string methods. It determines whether a string contains a specific substring and returns true if the substring is found and false otherwise.
How to use includes()?
To use includes(), you can call it on any string object and pass the substring you want to search for as an argument. Here's an example:
const str = "JavaScript is amazing!";
const includesWord = str.includes("amazing");
console.log(includesWord); // Output: trueIn this example, the includes() method checks whether the string str contains the word "amazing". Since it does, the method returns true.
Practical Use Case: Keyword Search in Text
Imagine you have a search feature in your web application, and you want to check whether a user's query contains specific keywords. You can use includes() for this purpose:
function isKeywordInQuery(query, keyword) {
return query.includes(keyword);
}
const userQuery = "JavaScript tutorial";
const keywordToSearch = "JavaScript";
const isFound = isKeywordInQuery(userQuery, keywordToSearch);
console.log(isFound); // Output: trueHere, the isKeywordInQuery() function checks whether the userQuery includes the keywordToSearch. If it does, it returns true, indicating that the keyword was found in the query.
Frequently Asked Questions (FAQs)
LSI (Latent Semantic Indexing) Keywords are terms and phrases that are related to the main topic or primary keyword. Yes, using LSI Keywords in your headings can be beneficial as it provides context to search engines about the content's relevance and improves the overall SEO performance.
No, startsWith() is a string method and can only be used on strings.
endsWith() method considers whitespace as part of the string. For example, "Hello, world!" and "Hello, world! " (with a space at the end) are treated as different strings.
Yes, includes() is case-sensitive. It will return true only if the substring's case matches exactly with the case in the original string.
No, these methods are specific to string data types in JavaScript. Attempting to use them on non-string data may result in errors.
No, all three methods (startsWith(), endsWith(), and includes()) are non-destructive, meaning they do not modify the original string. Instead, they return a new boolean value based on the search criteria.
Conclusion
In this JavaScript Tutorial-75: String Methods | Startswith, Endswith, Includes, we explored three essential string methods that are incredibly useful in web development. We learned how to use startsWith(), endsWith(), and includes() to check for specific substrings within a string.
Remember, mastering these string methods will not only make your code more efficient but also enhance your overall JavaScript skills. Whether you need to validate URLs, search for keywords, or perform text manipulations, these methods will come to your rescue.
So, keep practicing and incorporating these string methods into your projects to become a proficient JavaScript developer.
