#js_engine

#Features

• Numeric literals (IEEE 754 doubles), strings, booleans, null, undefined
• Variable declarations: let, const, var
• Arithmetic: +, -, *, /, %
• Comparison: <, >, <=, >=
• Equality: ==, ===, !=, !==
• Logical: &&, ||, !
• Control flow: if/else, while, for, break, continue, return
• Functions: declarations, expressions, closures, recursion
• Ternary operator: ? :
• typeof operator
• console.log() output
• String concatenation (including mixed types)
• Single-line (//) and multi-line (/* */) comments

#Package Structure

token/          Token types and source locations
lexer/          Tokenizer
ast/            AST node definitions
parser/         Recursive descent parser with Pratt precedence
interpreter/    Tree-walking evaluator with closures and scope chains
cmd/main/       CLI entry point

#Usage

#CLI

moon run cmd/main -- 'console.log(1 + 2)'
# 3

moon run cmd/main -- '
function fib(n) {
  if (n <= 1) { return n; }
  return fib(n - 1) + fib(n - 2);
}
console.log(fib(10));
'
# 55

#As a Library

let (output, result) = @js_engine.run("console.log(1 + 2)")
// output = ["3"], result = "undefined"

#Development

moon check        # Type check
moon fmt          # Format code
moon info         # Update .mbti interface files
moon test         # Run tests
moon test --update # Update snapshot tests
moon build        # Build

#Documentation

• ROADMAP.md — Current test262 status, failure breakdown, future targets, architecture overview
• docs/PHASE_HISTORY.md — Archived implementation notes for completed phases (1-6)
• AGENTS.md — MoonBit coding conventions and tooling guide for AI agents

#License