Every Project Should Have Its Own REPL

Amjad Masad

It's no secret we're big fans of REPLs. We believe that immediate access to the programming environment accelerates learning and is generally more productive. REPLs cut out the middleman -- no need to build UIs or scripts for every possible action you might want to take -- just talk to the interpreter directly.[](preview end)

In every medium-to-large project we embark on we include a repl.sh script that starts out a REPL in the context of the project. This includes preloaded libraries, custom commands, and a database connection when it makes sense. You can interact with the database, use utility functions, and inspect the environment in whatever way you find useful.


This is especially easy in NodeJS; the module that makes up the REPL that ships with it is made into a stand-alone module repl. Once you require('repl') you'll be able to supply it with a custom eval function which you can then use to process the and parse the code in whatever way you find useful before calling a callback with a return value.

We love using async/await so we process top-level awaits with babel in the REPL to make it very easy to add, update, or delete from the development database. In the above gif you can see how we can test and iterate on our notifications page by creating notifications from the REPL and see it update instantly!

To conclude, we encourage you to create shells and REPLs for your projects, it's an easy productivity win!

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