jsbasic - Applesoft BASIC in JavaScript
This is hosted for playing with at https://inexorabletash.github.io/jsbasic/
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 thingsHSCRN(x, y) allows probing the hi-res screen- hexadecimal literals e.g.
$C010 can be used as numbers