JavaScript - UnderScore

UnderScore 第一步 call(this)

 (function() {}.call(this));

一些简单的初始化操作

 (function() {
  var root = this;
  var previousUnderscore = root._;

var ArrayProto = Array.prototype,
  ObjProto = Object.prototype,
  FuncProto = Function.prototype;
var
  push = ArrayProto.push,
  slice = ArrayProto.slice,
  concat = ArrayProto.concat,
  toString = ObjProto.toString,
  hasOwnProperty = ObjProto.hasOwnProperty;

var nativeIsArray = Array.isArray,
  nativeKeys = Object.keys,
  nativeBind = FuncProto.bind;

  }.call(this));

下划线出场 创建对象

var _ = function(obj) {
  if (obj instanceof _) return obj;
  if (!(this instanceof _)) return new _(obj);
  //this._wrapped = obj;  //do not need this at first.
};