The extend in backbone and underscore

Always confuse the extend in these two libraries, so write it down.

The extend in backbone implements inheritance:

1   //Helper function to correctly set up the prototype chain for subclasses.2   //Similar to ' goog.inherits ', but uses a hash of prototype properties and3   //class properties to be extended.4   varExtend =function(Protoprops, staticprops) {5     varParent = This;6     varChild ;7 8     //The constructor function for the new subclass was either defined by9     //(the "constructor" property is in your ' extend ' definition), or defaultedTen     //By us to simply call the parent constructor. One     if(Protoprops && _.has (Protoprops, ' constructor ')) { AChild =Protoprops.constructor; -}Else { -Child =function(){returnParent.apply ( This, arguments); }; the     } -  -     //Add Static properties to the constructor function, if supplied. - _.extend (Child, parent, staticprops); +  -     //Set The prototype chain to inherit from ' parent ', without calling +     //' Parent ' s constructor function and add the prototype properties. AChild.prototype =_.create (Parent.prototype, protoprops); atChild.prototype.constructor =Child ; -  -     //Set A convenience property in case the parent's prototype is needed -     //later. -child.__super__ =Parent.prototype; -  in     returnChild ; -   }; to  +   //Set up inheritance for the model, collection, router, view and history. -Model.extend = Collection.extend = Router.extend = View.extend = History.extend = Extend;

View Code

The extend in underscore enables shallow replication:

1_.extend =Createassigner (_.allkeys);2 3 varCreateassigner =function(Keysfunc, undefinedonly) {4     return function(obj) {5       varLength =arguments.length;6       if(Length < 2 | | obj = =NULL)returnobj;7        for(varindex = 1; Index < length; index++) {8         varSource =Arguments[index],9Keys =Keysfunc (source),TenL =keys.length; One          for(vari = 0; I < L; i++) { A           varKey =Keys[i]; -           if(!undefinedonly | | obj[key] = = =void0) Obj[key] =Source[key]; -         } the       } -       returnobj; -     }; -};

View Code

The extend in backbone and underscore