jslint-org/jslint

JSLint is a tool that reads JavaScript code and tells you what is wrong with it. Created by Douglas Crockford, one of the early architects of JavaScript, it has been around in various forms for over a decade and has a reputation for being strict. The idea is simple: you hand it a JavaScript file, it analyzes the code, and it reports any problems it finds. The tool is distributed as a single file called jslint.mjs with no external dependencies and no configuration required out of the box. You download that one file, point it at your JavaScript, and it works. You can run it from the command line, import it into another JavaScript program, or use it through editor plugins for Vim and VSCode. There is also a web demo at jslint.com where you can paste code and see results immediately without installing anything. Beyond catching code quality issues, JSLint can also generate coverage reports. Coverage tells you which parts of your code actually ran during a test, so you can see what was never tested. It connects to Node.js's built-in coverage data to produce these reports without requiring a separate coverage tool. For teams or individuals who want automatic quality checks, JSLint can be run across an entire directory of files in one command, making it practical for larger projects. It includes a range of optional directives you can add as comments inside your code to tell JSLint about your environment, such as whether the code runs in a browser or on a server, and to relax or tighten specific rules. The project is maintained actively, with a version number that matches the release date, and it runs automated checks across three branches to verify each change before it ships.