@thi.ng/grid-iterators/spiral.js

2D grid and shape iterators w/ multiple orderings

import { __opts } from "./utils.js";
function* spiral2d(opts) {
  const { cols, rows, tx } = __opts(opts);
  const num = cols * rows;
  const center = Math.min(cols, rows) - 1 >> 1;
  for (let i = 0; i < num; i++) {
    let nx = cols;
    let ny = rows;
    while (i < nx * ny) {
      nx--;
      ny--;
    }
    const nxny = nx * ny;
    const minnxny = Math.min(nx, ny);
    const m2 = minnxny >> 1;
    let bx, by;
    if (minnxny & 1) {
      if (i <= nxny + ny) {
        bx = nx - m2;
        by = -m2 + i - nxny;
      } else {
        bx = nx - m2 - (i - (nxny + ny));
        by = ny - m2;
      }
    } else {
      if (i <= nxny + ny) {
        bx = -m2;
        by = ny - m2 - (i - nxny);
      } else {
        bx = -m2 + (i - (nxny + ny));
        by = -m2;
      }
    }
    yield tx(bx + center, by + center);
  }
}
export {
  spiral2d
};