nolanlawson/optimize-js

optimize-js is a command-line tool that processes JavaScript files to make them load faster in a browser, specifically by reducing the time the browser spends parsing the code. The author explicitly marks it as unmaintained and notes that the V8 team (the people behind Chrome's JavaScript engine) have published a post explaining why it is no longer the right approach for modern browsers. To understand what the tool does, it helps to know how browsers handle JavaScript files. When a browser loads a JS file, the engine does not fully process every function immediately. Instead, it does a quick pre-scan of most functions, only doing the full work when a function is about to be called. This saves time on average, because many functions in a typical file are never called or are called much later. The problem is that some functions are meant to run immediately when the file loads, and the browser does not always detect this correctly. When it misses, it pre-scans the function and then fully parses it again, doubling the work. optimize-js reads a JavaScript file before you deploy it, figures out which functions are meant to run immediately, and wraps them in parentheses. This is a known signal that browsers recognize: a function inside parentheses is likely to run right away, so the engine skips the pre-scan and goes straight to the full parse. The result is that the same function is only processed once instead of twice, which speeds up how quickly the page becomes usable. Benchmarks at the time of the project's active development showed speed improvements of roughly 8 to 20 percent across Chrome, Edge, and Firefox for common JavaScript libraries like React, jQuery, and Lodash. Safari showed a slight regression. The tool was most useful when applied after minification, since minifiers tend to remove the parentheses that trigger the optimization. Installation is through npm, and use is a single command: feed it an input file and redirect the output.