Due to the rapid spread of EC sites and tech products in recent years, many people have come to use Web services. As a result, front-end engineers are required to have the skills to build UIs that are easier for users to use than in the past. The JavaScript framework library is useful for building such a UI. If you are a front-end developer, or trying to become a front-end developer, fluency with HTML, CSS and JavaScript is way not enough. Why? Nowadays, companies worldwide are using framework libraries to efficiently create responsive websites. Therefore, you need to get your skill set enhanced / updated with the very useful frameworks / libraries. Let's check together 3 must-learn frameworks / libraries for front-end developers! 1. React.js React.js is an open source JavaScript library developed by Facebook. React.js allows us to break down the complex UI into simpler components, therefore we can install it in any web application without rewriting the existing source code. React.js is gaining so much popularity these days because of its extra simplicity and flexibility. Some of the big names using React.js to solve UI related issues are Facebook, PayPal, Uber, Instagram and Airbnb. React.js assures of better performance with cost efficiency now and then, thanks to the commitment of Facebook and the entire React.js team to improve its features. 2. Vue.js Vue.js is another framework owned by Google, which retains only the good points of "older brother" Angular.js . With Vue.js, you can migrate your existing projects one feature at a time. Its simple structure also helps learners to learn and apply into development quickly, therefore the cost could be lower with faster progress. Over the last couple of years, Vue.js became extremely popular among developers and gained official support from Laravel. Here is a brief sum-up and comparison between React.js and Vue.js. from: www.rockersinfo.com 3. jQuery jQuery is a lightweight, "write less, do more", JavaScript library. The purpose of jQuery is to make it much easier to use JavaScript on your website. jQuery takes a lot of common tasks that require many lines of JavaScript code to accomplish, and wraps them into methods that you can call with a single line of code. Recently, the risings of Vue.js, React.js and Angular.js etc. has effected the popularity of jQuery. Still, according to jQuery's survey, jQuery is still in use on a staggering 73% percent of 10 million popular websites. Summary When you're a developer, your job requires you to learn every single day. One of the rules for developers to learn efficiently and effectively is that you should learn what is widely used, which you can easily apply on your work or your personal projects. If you complete learning and gain some experience with Vue.js, React.js and jQuery, you sure can perform better in your current position, or land an good opportunities.