In the previous chapter, we excluded some important functions that are essential in implementing the method-chaining concept. Underscore has built-in support for this concept through the _.chain(obj) function, which returns a new instance of the _ object with the obj parameter stored as a property of the returned object; this property is called _wrapped. The new _ instance is different from the global _ object exclusively used up until now in all our examples. The new _ instance becomes the vehicle of the method chain started with _.chain(obj) and we can use it to call any Underscore function without specifying the first argument. The first argument is always implied to be the _wrapped instance, so we can write code like this:

var people = [{
  name: "Herta Muller",
  birthYear: 1953,
  awardYear: 2009
}, {
  name: "Mario Vargas Llosa",
  birthYear: 1936,
  awardYear: 2010
}, {
  name: "Tomas Transtromer",
  birthYear: 1931,
  awardYear: 2011
}, ...