Convert user input string into regular expression using JavaScript Last Updated : 28 Apr, 2023 Summarize Comments Improve Suggest changes Share Like Article Like Report In this article, we will convert the user input string into a regular expression using JavaScript.To convert user input into a regular expression in JavaScript, you can use the RegExp constructor. The RegExp constructor takes a string as its argument and converts it into a regular expression object Regular expressions (RegExp) are patterns used to match character combinations in strings. In JavaScript, regular expressions are also objects. There are two ways to construct a regular expression in JavaScript. Using a regular expression literal, which consists of a pattern enclosed between slashes, as follows. const reg = /ab+/; Calling the constructor function of the RegExp object, as follows. const reg = new RegExp('ab+', flag); Using the constructor function provides run time compilation of the regular expression, hence we should use the second method here as the string is a dynamic input from the user. Both the above expressions correspond to the same RegExp. Example 1: For the string, we will take "Geeks For Geeks'". Input : '^Ge' Output: ["Ge"] 0: "Ge" Input : '[A-z]+' Output: (3) ["Geeks", "For", "Geeks"] 0: "Geeks" 1: "For" 2: "Geeks" JavaScript const str = "Geeks for Geeks"; // Input from User const regex = prompt("Enter RegExp"); // Conversion from string to RegExp const reg = new RegExp(regex, "g"); // The match fn returns the array of strings // That match to RegExp const result = str.match(reg); if (result) console.log(result); else console.log("Not Found"); Output: Example 2: In this example, we will use the RegExp constructor. JavaScript const userInput = prompt("Enter a regular expression pattern:"); const regex = new RegExp(userInput); console.log(regex); Output: Comment More infoAdvertise with us K ksucheta19 Follow Improve Article Tags : JavaScript Web Technologies javascript-string regular-expression JavaScript-Questions +1 More Similar Reads Non-linear Components In electrical circuits, Non-linear Components are electronic devices that need an external power source to operate actively. Non-Linear Components are those that are changed with respect to the voltage and current. Elements that do not follow ohm's law are called Non-linear Components. Non-linear Co 11 min read JavaScript Tutorial JavaScript is a programming language used to create dynamic content for websites. It is a lightweight, cross-platform, and single-threaded programming language. It's an interpreted language that executes code line by line, providing more flexibility.JavaScript on Client Side: On the client side, Jav 11 min read Web Development Web development is the process of creating, building, and maintaining websites and web applications. It involves everything from web design to programming and database management. Web development is generally divided into three core areas: Frontend Development, Backend Development, and Full Stack De 5 min read Spring Boot Tutorial Spring Boot is a Java framework that makes it easier to create and run Java applications. It simplifies the configuration and setup process, allowing developers to focus more on writing code for their applications. This Spring Boot Tutorial is a comprehensive guide that covers both basic and advance 10 min read React Interview Questions and Answers React is an efficient, flexible, and open-source JavaScript library that allows developers to create simple, fast, and scalable web applications. Jordan Walke, a software engineer who was working for Facebook, created React. Developers with a JavaScript background can easily develop web applications 15+ min read React Tutorial React is a powerful JavaScript library for building fast, scalable front-end applications. Created by Facebook, it's known for its component-based structure, single-page applications (SPAs), and virtual DOM,enabling efficient UI updates and a seamless user experience.Note: The latest stable version 7 min read JavaScript Interview Questions and Answers JavaScript is the most used programming language for developing websites, web servers, mobile applications, and many other platforms. In Both Front-end and Back-end Interviews, JavaScript was asked, and its difficulty depends upon the on your profile and company. Here, we compiled 70+ JS Interview q 15+ min read Class Diagram | Unified Modeling Language (UML) A UML class diagram is a visual tool that represents the structure of a system by showing its classes, attributes, methods, and the relationships between them. It helps everyone involved in a projectâlike developers and designersâunderstand how the system is organized and how its components interact 12 min read Backpropagation in Neural Network Back Propagation is also known as "Backward Propagation of Errors" is a method used to train neural network . Its goal is to reduce the difference between the modelâs predicted output and the actual output by adjusting the weights and biases in the network.It works iteratively to adjust weights and 9 min read 3-Phase Inverter An inverter is a fundamental electrical device designed primarily for the conversion of direct current into alternating current . This versatile device , also known as a variable frequency drive , plays a vital role in a wide range of applications , including variable frequency drives and high power 13 min read Like