jsbasic - Applesoft BASIC in JavaScript

Use git clone --recursive to get polyfill for older browsers.

Notes & Known Issues

The BASIC program is compiled to JavaScript before execution. Syntax errors are therefore detected at compile-time rather than at run-time as on a traditional interpreter. For example, the following program would run without errors on an Apple since the erroneous second statement is never reached. 10 END : CHR$(PRINT)
Handling of BASIC code that does not match the canonical LIST output format may not behave as on an Apple:
- Keyword parsing differs from Applesoft command line. For example FOR I = S TO P doesn't collapse into FOR I = STOP.
Limitations:
- Floating point overflow is only detected on variable assignment.
- Only a subset of DOS 3.3 and ProDOS useful for basic file I/O are implemented.
- Only a small number of common PEEK, POKE and CALL locations are supported.
- Commands that refer to assembly routines (&, USR() etc.), shape tables, and tape I/O are not implemented.
Commands that operate on the program itself (LIST, RUN, DEL, etc.) are not implemented.
A handful of extensions are made beyond Applesoft BASIC:
- To improve readability, lines may start with : and continue the previously numbered line.
- DEF FN can define string functions
- == can be used as =
- CHR$() values > 255 do interesting things
- HSCRN(x, y) allows probing the hi-res screen
- hexadecimal literals e.g. $C010 can be used as numbers

You can run your basic programs from the command line (with only basic text input and output, and no graphics or DOS commands):

Clone the repository locally
On Windows, run from a command prompt via: cscript.exe cbasic.js your_program.txt
On Mac/Linux, install Mozilla Rhino, run from the command prompt via: java -jar PATH_TO/js.jar cbasic.js your_program.txt