All JavaScript objects inherit properties and methods from a prototype.
In the previous chapter we learned how to use an object constructor:
Example
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
const myFather = new Person("John", "Doe", 50, "blue");
const myMother = new Person("Sally", "Rally", 48, "green");
We also learned that you can not add a new property to an existing object constructor:
Example
To add a new property to a constructor, you must add it to the constructor function:
Example
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
this.nationality = "English";
}
Prototype Inheritance
All JavaScript objects inherit properties and methods from a prototype:
Dateobjects inherit fromDate.prototypeArrayobjects inherit fromArray.prototypePersonobjects inherit fromPerson.prototype
The Object.prototype is on the top of the prototype inheritance chain:
Date objects, Array objects, and Person objects inherit from Object.prototype.
Adding Properties and Methods to Objects
Sometimes you want to add new properties (or methods) to all existing objects of a given type.
Sometimes you want to add new properties (or methods) to an object constructor.
Using the prototype Property
The JavaScript prototype property allows you to add new properties to object constructors:
Example
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.nationality = "English";
The JavaScript prototype property also allows you to add new methods to objects constructors:
Example
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.name = function() {
return this.firstName + " " + this.lastName;
};
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