ccharts

Turns financial OHLC data into a string — line and candlestick charts drawn with Unicode block characters. Nothing is printed for you, so the chart goes wherever text goes: a terminal, a log line, a chat message, an HTML <pre>, a file.

This is the C library ccharts compiled to WebAssembly. One package works everywhere — Node, Deno, Bun and the browser — with no native build step, no prebuilt binaries and no dependencies. The .wasm is embedded in the JavaScript, so there is nothing to fetch and no bundler configuration.

npm install ccharts

import { Chart, Color } from "ccharts";

const chart = Chart.fromArrays(open, high, low, close, epochSeconds);

console.log(chart.line({
  width: 60, height: 8,
  riseColor: Color.blue,
  showPrices: true,
  showTimes: true,
}));
console.log(chart.candle({ width: 60, height: 8 }));

chart.free();

• Data can also come from Chart.fromJson (fixed-schema JSON) or Chart.fromCsv.
• Color holds the sixteen ANSI colors; any escape string works, so 256-color and truecolor do too: { riseColor: "\x1b[38;5;208m" }.
• { plain: true } renders with no ANSI escapes at all, for output that is not going to a terminal.
• Plain arrays, Float64Array and BigInt64Array are all accepted.
• free() releases the WebAssembly memory. A FinalizationRegistry covers a forgotten call, but it runs whenever the GC feels like it.

Errors are CchartsError with a numeric code (1 invalid argument, 2 parse, 3 out of memory, 4 non-finite value, 5 bad dimensions).

Notes

• ESM only. The package uses top-level await to instantiate the WebAssembly module at import time, so import { Chart } from "ccharts" needs no initialization call. There is no CommonJS build.
• Node 18+ for TextDecoder, FinalizationRegistry and top-level await.
• Rebuilding the WebAssembly module (npm run build) needs emscripten; src/wasm-binary.js is checked in, so only contributors touching the C sources need it.

License

MIT — see the repository.