Http://www.jb51.net/article/25027.htm
http://blog.csdn.net/chunqiuwei/article/details/22092551
Http://developer.51cto.com/art/200907/134913.htm
Summarize:
Special note: Only the constructor has the prototype property, and the instance of the constructor does not have that property, that is, Console.log (a1.prototype) outputs the undefined. In JavaScript, each function automatically has a prototype property, not every object has a prototype property
The prototype attribute is not related to the creation of an instance object, it already exists before the object is created
It is possible to conclude that there are predefined constructor properties in the object pointed to by the prototype property, and that each instance of the constructor inherits this property, so without overriding the prototype object, The constructor of the instances point to their constructors
Prototype and constructor in JavaScript