get properties of an object;

get_props_if.js

// get properties of an object;
// if f(property) is true;
var get_props_if = function (obj, f) {
  f = f || function (arg) {return true;};
  var holder = [];

  for (var p in obj) if (f.call(obj, p)) {
    holder.push(p);
  }

  return holder;
}

console.log(get_props_if(p, {}.hasOwnProperty));
console.log(get_props_if(a));