Function d3_functor

d3-3.2.8/d3.js:1704–1708

(v)

    d3_rgb_names.set(key, d3_rgbNumber(value));
  });
  function d3_functor(v) {
    return typeof v === "function" ? v : function() {
      return v;
    };
  }
  d3.functor = d3_functor;
  function d3_identity(d) {
    return d;