What is meaning of domain and default function in javascript?

Question

What is meaning of defaults: function($super) and domain: function($super) in javascript?. The following code is taken from openstack-horizon. They are using very high level of javascript concept but I know basic of javascript.

Rickshaw.Graph.Renderer.StaticAxes = Rickshaw.Class.create(Rickshaw.Graph.Renderer.Line, {      
  name: 'StaticAxes',
  defaults: function($super) {
    alert("13 => This is repeated many time. Rickshaw.Graph.Renderer.StaticAxes");
    return Rickshaw.extend($super(), {
      xMin: undefined,
      xMax: undefined,
      yMin: undefined,
      yMax: undefined
    });
  },
  domain: function($super) {
    //alert("HJ");
    var ret = $super();
    var xMin, xMax;
    // If y axis wants to have static range, not based on data
    if (this.yMin !== undefined && this.yMax !== undefined) {
      ret.y = [this.yMin, this.yMax];
    }
    // If x axis wants to have static range, not based on data
    if (this.xMin !== undefined && this.xMax !== undefined) {
      xMin = d3.time.format.utc('%Y-%m-%dT%H:%M:%S').parse(this.xMin);
      xMin = xMin.getTime() / 1000;
      xMax = d3.time.format.utc('%Y-%m-%dT%H:%M:%S').parse(this.xMax);
      xMax = xMax.getTime() / 1000;

      ret.x = [xMin, xMax];
    }
    return ret;
  }
});

Answer 1

Consider this code.

var objectLiteral = {
    variable: "I'm a string",
    fun: function(param) {
        console.log("I'm a function.");
        console.log("Here's the param: ", param);
    }
}

console.log(objectLiteral);
objectLiteral.fun();

fun and variable are fields of the object literal.
function() syntax is used to declare a function, which get assigned to fun.