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Janet (Wasm)

Janet is a lightweight, embeddable, Lisp-like (Clojure-like), dynamically typed programming language.

In LiveCodes, Janet runs in the browser on the Janet interpreter compiled to WebAssembly, entirely client-side. No server is involved.

Usage​

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "config": {
    "activeEditor": "script",
    "script": {
      "language": "janet-wasm",
      "content": "(print \"Hello, World!\")"
    },
    "mode": "simple",
    "editor": "auto",
    "tools": {
      "status": "full"
    }
  }
};
createPlayground('#container', options);

Standard I/O​

The program runs on the result page. Anything it prints is captured and shown in the console. Standard input is passed by setting the livecodes.janetWasm.input property in JavaScript before the program runs. It is read in Janet with (file/read stdin :all) and friends; a program that never reads never notices it was there. To run again with new input, call livecodes.janetWasm.run(input).

Communication with JavaScript​

A few helper properties and methods are available in the browser global livecodes.janetWasm object:

  • livecodes.janetWasm.input: the standard input passed to the program.
  • livecodes.janetWasm.loaded: a promise that resolves when the interpreter has downloaded and the program has run once. It rejects if the runtime fails to load. Other helpers should be used after it resolves.
  • livecodes.janetWasm.output: the program's output, standard output and standard error in the order the program wrote them.
  • livecodes.janetWasm.error: the interpreter diagnostics, if the program failed.
  • livecodes.janetWasm.exitCode: the exit code of the program (0 ok, 1 runtime error, 2 compile error, 4 parse error).
  • livecodes.janetWasm.run(input): runs the code again with new input, returning a promise that resolves to { output, error, exitCode }.

Example:

show code
import { createPlayground } from 'livecodes';

const options = {
  "template": "janet-wasm",
  "params": {
    "activeEditor": "markup"
  }
};
createPlayground('#container', options);

Language Info​

Name​

janet-wasm

Aliases / Extensions​

janet, wasm.janet

Editor​

script

Compiler​

The Janet interpreter compiled to WebAssembly (built with Emscripten), packaged by @live-codes/janet-wasm.

Version​

Janet 1.42.1.

Code Formatting​

Not currently supported.

Live Reload​

By default, new code changes are sent to the result page for re-evaluation without a full page reload, avoiding the need to reload the interpreter. This behavior can be disabled by adding the code comment # __livecodes_reload__ to the Janet code, which forces a full page reload.

This comment can be added in the hiddenContent property of the editor for embedded playgrounds.

Example Usage​

(defn fib [n]
  (if (< n 2)
    n
    (+ (fib (- n 1)) (fib (- n 2)))))

(each n (range 10)
  (prin (fib n) " "))
(print)

Each run is independent: definitions from one run do not survive into the next.

Starter Template​

https://livecodes.io/?template=janet-wasm

Sponsors