Implement your own runtime system


What is so-called runtime?

> node main.js
  • Understand JavaScript syntax
  • Execute your JavaScript program
  • Provide native APIs for your JavaScript program to do things like File I/O
  • Manage the memory consumed by your JavaScript program

Our Goal

By tiny

  1. Primitive types: number, string, bool.
  2. Compound types: array with `.map` and `.reduce`.
  3. Expressions: case/switch, function call, operators.
  4. No statements inside the Function, except for variable declaration.
  5. Lazy by default (realized by returning Functions, instead of values).
  6. Pluggable “context” as native modules and can use `require` syntax to consume them.
  7. (Optional) File-based module system (still support `import`).

By fork-able

You can experiment with this runtime whatever you like!

By understandable

You can see what’s going on when your program is being executed.

Our Architecture

runtime architecture

Guest Language

Host Language



Just-In-Time compiler (JIT)



Garbage Collector

Runtime APIs




Frontend Developer @Mercari, who does sports and philosophy.

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Paipo Tang

Paipo Tang

Frontend Developer @Mercari, who does sports and philosophy.

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