Not actually Javascript, but there's no "processing" option in the Language dropdown for a gist

gistfile1.js

void dump_image() {
  beginShape(POINTS);

  int i;
  for(i=0; i<cols.length; i++) {
    stroke(cols[i]);
    vertex(xs[i], ys[i], zs[i]);
    if(numPoints != 0 && i%numPoints ==0) {
      endShape();
      beginShape(POINTS);
    }
  }

  endShape();
}