rojs/dist/example.js

const CANVAS_ID = "canvas";
const GAT_FILE_ID = "gat_file";

const canvas = document.getElementById(CANVAS_ID);
if (canvas === null) {
  throw new Error("couldn't find element #" + CANVAS_ID);
}

const gl = canvas.getContext("webgl");
if (gl === null) {
  throw new Error("couldn't initialize webgl context");
}

gl.clearColor(0, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);

if (typeof window.rojs !== "object") {
  throw new Error("ro.js not found, is it loaded?");
}

const gatFile = document.getElementById(GAT_FILE_ID);
gatFile.addEventListener("change", (e) => {
  const file = gatFile.files[0];
  const reader = new FileReader();

  reader.onload = (e) => {
    const gat = window.rojs.parseGAT(e.target.result);
    window.rojs.renderGAT(gl, gat);
  };

  reader.readAsArrayBuffer(file);
});