Source maps describe how the compiled code is related to your original source code. The debugger can then show the original code you wrote, while actually running the compiled code.
The file specifies the mapping version used and identifies the source files and names of parameters. The useful part is the mappings, although unfortunately since they are in Base 64 VLQ, they’re not very useful for the human brain.
If you’d like to understand more about how the mappings work, and how they translate the minified code back to the source, I’d recommend reading How do source maps work. For now, let’s look at how to leverage the source map in production to make debugging easier.
If you open the index.html in Chrome or your browser of choice, you’ll notice that there is a JavaScript error which is thrown on the first line of our minified file. Let’s make it easier to identify and resolve this.