Explore the Underscore.js library by example using a test-driven development approach About This Book Understand and learn to apply functional programming principles using the built-in functions of Underscore.js Leverage and reuse Underscore.js-base
Underscore.js is one of the most popular modern Javascr ipt libraries used for functional programming. It can be used as a base for building complex Javascr ipt applications in a sustainable manner and for building other Javascr ipt libraries. It em
underscore.js
敲underscore.js源码（function（）{// BASELINE SETUP
/*Establish the root object,window in the browser,or export on the server:创建一个全局对象，在浏览器中表示window对象，在Node.js中表示global对象:var root=this;*/
var root = this;
/*Save the previous value of the _ v
