Javascript Prototype

Every JS object has a prototype.

All JS objects inherit their properties/methods from their prototype.

The standard way to create an object prototype is to use object constructor function:

function person(first, last age) {  
    this.firstName = first;
    this.lastName = last;
    this.age = age;
};

var farther = new person("Frank", "Zhang", 40);

farther.Country = "Canada"; //Add methods/property to the exist object

father.name = function () {
    return this.firstName + " " +this.lastName;
}

You can extend the object with new function and new properties as above. However, the new added function/property are limited only for the class you defined as above.

If you want to add function/property for all person object, you need to user prototype.

person.prototype.name = function () {
    return this.firstName + " " + this.lastName;
};

Last but not least, Never modify the prototypes of Standard Javascript Objects.