It goes without saying that a Javascript developer should have experience with HTML, CSS, and Javascript itself. Besides that, having familiarity or experience in various JS frameworks such as React, Angular, Vue, Node, etc. are an added advantage if you are going to use any of it in your project. Hands-on experience with various developer tools like Git, Webpack, NPM, etc., version controlling, problem-solving, understanding of data structures, and soft skills are some add ons to look for.