glcanvas/js/obj.js

function parseObj(docStr) {
    const bufPositions = [];
    const bufNormals = [];

    const out = [];

    var vertCount = 0;

    const ops = {
        v(str) {
            var xyz = str.match(/[0-9.-]+/g).map(Number);
            bufPositions.push(xyz);
        },
        vn(str) {
            var xyz = str.match(/[0-9.-]+/g).map(Number);
            bufNormals.push(xyz);
        },
        f(str) {
            const pts = [];

            for (var faceStr of str.split(" ")) {
                var [iV, iVt, iVn] = faceStr.split("/").map(Number);

                /* obj uses 1-based indices */
                iV--; iVt--; iVn--;

                pts.push({
                    iV: iV,
                    // iVt: iVt,
                    iVn: iVn,
                });
            }

            /* triangulate. */
            for (var i = 0; i < pts.length - 2; i++) {
                out.push(
                    bufPositions[pts[0].iV],
                    bufNormals[pts[0].iVn],
                    bufPositions[pts[i + 1].iV],
                    bufNormals[pts[i + 1].iVn],
                    bufPositions[pts[i + 2].iV],
                    bufNormals[pts[i + 2].iVn],
                );
                vertCount += 3;
            }
        }
    };

    for (var line of docStr.split("\n")) { /* if you use crlf that sucks lol */
        if (line == "" || line.startsWith("#")) {
            continue;
        }

        var tks = line.split(" ");
        var op = tks.shift();
        var cont = tks.join(" ");

        var opFunc = ops[op];
        if (opFunc) opFunc(cont);
    }

    return [new Float32Array(out.flat()), vertCount];
}