A function that extends an object given a path of properties, e.g. `opath(obj, 'one', 'two', 'three', null)`. Requires underscore.js to be available at `us`.

opath.js

function opath(){

  var args = Array.prototype.slice.call(arguments);

  var object = args.shift()
    , val = args.pop();

  if(args.length > 0){
    us.each(args, function(arg, i){
      var cur;
      if(i === 0){
        cur = object;
      }else{
        cur = eval('object["' + args.slice(0, i).join('"]["') + '"]');
      }
      if(!us.has(cur, arg) && i+1 === args.length){
        eval('object["' + args.slice(0, i+1).join('"]["') + '"] = val');
      }else if((us.has(cur, arg) && !us.isObject(cur[arg])) || !us.has(cur, arg)){
        eval('object["' + args.slice(0, i+1).join('"]["') + '"] = {}');
      }
    })
  }else{
    object = val;
  }

}