Object construction differences
Correct, the lifetime of objectSettings is only for the MyObject function, so you don't need the assignment to null at the end.

Passing in an object to the constructor is a common pattern to set its properties, and if you don't want to add specific assignment statements for each property, you can do something like this:

Utils = {
  // Taken from the ExtJS library
  apply: function(o, c, defaults) {
    if(defaults) {
      Utils.apply(o, defaults);
    }
    if(o &amp;&amp; c &amp;&amp; typeof c == 'object') {
      for(var p in c) {
        o[p] = c[p];
      }
    }
    return o;
  }
};

function MyObject(cfg) {
  Utils.apply(this, cfg, {
    id: 0,
    legs: 2,
    ...
  });

  // You now have access to this.id, etc.
}