BASIC To JavaScript Compiler

Created by opencode: This entire project was created by opencode, using a personal fork(https://github.com/panwar-stack/opencode) with 1 agent team and 64 autonomous DAG agents.

This project is a small BASIC-to-JavaScript compiler implemented in plain JavaScript for Node.js. It reads one .bas source file, compiles a deterministic line-label BASIC subset inspired by GW-BASIC and QuickBASIC, and emits readable self-contained JavaScript that runs directly with Node.js.

CLI Usage

Compile a BASIC file to JavaScript:

node src/cli.js compile examples/hello.bas --out dist/hello.js

Run the generated JavaScript:

node dist/hello.js

Compile and run the interactive example with piped stdin:

node src/cli.js compile examples/guess.bas --out dist/guess.js
printf '7\n' | node dist/guess.js

Print CLI help:

node src/cli.js --help

The first-pass CLI intentionally supports only compile <input.bas> --out <output.js>. It creates parent directories for --out, exits with code 0 on success, and exits with code 1 after printing diagnostics on compilation or file errors.

Supported BASIC Subset

The compiler supports one program per .bas file. Keywords and identifiers are case-insensitive, while string literal content is preserved.

Supported statements and syntax:

Feature	Support
Line labels	Optional numeric labels such as 10 PRINT "HI"
Statement separator	Colon, such as A = 1 : PRINT A
Comments	REM comment and apostrophe comments
Variables	Numeric variables such as A, COUNT, X1
String variables	Names ending in $, such as NAME$
Assignment	LET A = 1, A = 1, NAME$ = "Ada"
Output	PRINT, comma separator, semicolon separator
Input	INPUT A, INPUT A$, INPUT "Prompt"; A, INPUT "Prompt", A$
Branching	IF expr THEN statement, IF expr THEN lineNumber, optional ELSE
Jumps	GOTO lineNumber
Subroutines	GOSUB lineNumber, RETURN
Loops	FOR I = start TO end [STEP step], NEXT [I]
Arrays	One-dimensional DIM A(10) and DIM NAMES$(10)
Termination	END, STOP

Supported expressions:

numeric literals: 1, 1.5, .5
string literals: "hello"
arithmetic: + - * / ^
comparison: = <> < <= > >=
boolean: AND OR NOT
grouping: ( )
built-ins: ABS, INT, LEN, LEFT$, RIGHT$, MID$, STR$, VAL, RND

INPUT reads from standard input in generated JavaScript. Numeric targets parse one input line as a number and fail with a BASIC runtime error if the line is not numeric. String targets store the input line as text. Prompt strings are written before reading.

Unsupported Features

These classic BASIC features are intentionally out of scope for the first pass:

DATA, READ, RESTORE
ON GOTO, ON GOSUB
WHILE/WEND
DO/LOOP
SELECT CASE
DEF FN
SUB, FUNCTION
multi-dimensional arrays
OPTION BASE
file I/O
graphics
ON ERROR
RANDOMIZE

The CLI also does not include watch mode, multi-file compilation, source maps, package publishing, or an in-process run command.

Examples

examples/hello.bas:

10 PRINT "HELLO FROM BASIC"
20 END

examples/guess.bas:

10 PRINT "GUESS THE NUMBER"
20 INPUT "YOUR GUESS"; G
30 IF G = 7 THEN PRINT "RIGHT" ELSE PRINT "TRY 7"
40 END

The examples/suite/ directory contains a broader compiler-check suite that exercises the supported BASIC subset, including printing, comments, colon-separated statements, numeric and string expressions, built-ins, IF, GOTO, GOSUB, FOR/NEXT, arrays, INPUT, STOP, selected runtime errors, and larger programs that combine several features in one flow.

Run the automated examples checks with the full test suite:

npm test

Compile any suite example manually:

node src/cli.js compile examples/suite/12-arrays.bas --out dist/12-arrays.js
node dist/12-arrays.js

Tests

Run the full test suite:

npm test

Run the generated-code tests only:

npm test -- test/codegen.test.js

Compatibility Notes

This compiler favors deterministic generated JavaScript and clear diagnostics over full historical BASIC compatibility.

Known differences from classic BASIC:

• PRINT A, B uses one space between values instead of classic tab zones.
• Invalid numeric INPUT exits with a runtime error instead of reprompting.
• Arrays are one-dimensional and use inclusive bounds, so DIM A(10) permits indexes 0 through 10.
• RND() is deterministic in the first pass, and RANDOMIZE is not supported.
• Jumps into or out of a FOR/NEXT region are rejected to protect generated loop state.
• Generated JavaScript is self-contained except for Node built-ins needed by compiled programs, such as stdin handling for INPUT.