pfmt

A strongly-typed Deno module for formatting and printing to the console inspired by Rust’s format and println macros.

Usage

Import any members from this module via the deno.land/x registry:

import { format } from "https://deno.land/x/pfmt/mod.ts";

println("Hello, {}!", "user"); // "Hello, user!"

Walkthrough

pfmt is very similar to Rust’s println and format macros in the sense that you declare different “slots” (places where variables can go) within the first parameter via curly braces and then declare the values for the slots in the parameters after the slot template string. The format function returns a generated string from the given slot template and slot template variables and the println function logs out the equivalent format function with the given arguments.

format("Hello, {}!", "user"); // returns "Hello, user"
println("Hello, {}!", "user"); // logs "Hello, user"

Remember, you must include a slot variable for every single slot template you have within your first slot template string. I advise you to use TypeScript because it will auto-magically check if you are doing that correctly.

You can also specify if you want to use Deno.inspect for a given varibale by adding in :? as the slot type.

println("{}", { age: 23 }); // logs "[Object object]"
println("{:?}", { age: 23 }); // logs "{ age: 23 }"

pfmt maintains its type-soundness via TypeScript conditional types and generics. This allows us to verify at compile-time whether or not the correct template is being passed into println and format. Here is an example of this at use:

println("Hello, {}!"); // TypeScript Compile Error: expected 2 parameters got 1

println("Hello, {} {}!"); // TypeScript Compile Error: expected 3 parameters got 1

println("Mr. {}. Welcome back, we missed you.", "Anderson"); // no errors :) works as expected

Testing

Make sure you run deno test to check if any of the code is broken.

Contributing

Before you contribute, make sure you test and run deno fmt before committing.

License

MIT