JavaScript: Check if String Starts with Substring

Introduction

In this tutorial, we'll take a look at how to check if a string starts with a substring in JavaScript.

This is easily achieved either through the startsWith() method, or regular expressions.

Check if String Starts with Another String with startsWith()

The startsWith(searchString[, position]) method returns a boolean which indicates whether a string begins with the characters of a specified searchString. Optionally we can also use the position argument to specify the position of the string at which to begin searching.

Let's see this in action:

const str = "This is an example for startsWith() method";

console.log(str.startsWith("This")); // true
console.log(str.startsWith("is", 2)); // true

In the first example, we are checking if the string str starts with "This".

In the second example, we are checking if str starts with "is", if we are starting our search from index 2 (i.e, 3rd character).

Check if String Starts with Another String with Regular Expressions

Regular Expressions are really powerful, and allow us to match various patterns. This is a great use-case for them, since we're essentially checking for a pattern - if a string starts with a substring.

The regexObj.test(reg) method tries to match the specified regular expression reg to the original string and returns a boolean value which indicates if a match was found:

const str = "hello world";

const regEx = /^he/;

console.log(regEx.test(str)); // true

In this approach, we are checking whether the pattern regEx occurs in the string str. The ^ meta character represents that the specified pattern he must be at the start of a line. Thus, the regular expression - /^he/ checks if the specified line starts with the substring he.

Conclusion

In this tutorial, we've taken a look at how to check if a string starts with a substring in vanilla JavaScript, using the startsWith() method, as well as Regular Expressions.

Last Updated: October 4th, 2023
Was this article helpful?

Improve your dev skills!

Get tutorials, guides, and dev jobs in your inbox.

No spam ever. Unsubscribe at any time. Read our Privacy Policy.

Abhilash KakumanuAuthor

Hey, I am a full-stack web developer located in India. I am a curious person who is always trying to wrap my head around new technologies. In my free time, I read novels and play with my dog!

Project

React State Management with Redux and Redux-Toolkit

# javascript# React

Coordinating state and keeping components in sync can be tricky. If components rely on the same data but do not communicate with each other when...

David Landup
Uchechukwu Azubuko
Details

Getting Started with AWS in Node.js

Build the foundation you'll need to provision, deploy, and run Node.js applications in the AWS cloud. Learn Lambda, EC2, S3, SQS, and more!

© 2013-2024 Stack Abuse. All rights reserved.

AboutDisclosurePrivacyTerms