underscore.js _tap[Object]

Invokes interceptor with the object, and then returns object. The primary purpose of this method is to "tap into" a method chain, in order to perform operations on intermediate results within the chain

对象的拦截器，用于在对象方法链中，调试对象

_.chain([1,2,3,200])
  .filter(function(num) { return num % 2 == 0; })
  .tap(alert)
  .map(function(num) { return num * num })
  .value();
=> // [2, 200] (alerted)
=> [4, 40000]

源码:

  _.tap = function(obj, interceptor) {
    interceptor(obj);
    return obj;
  };