JavaScript/Inheritance

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instanceof operatorEdit

The instanceof operator determines if an object was instantiated as a child of another object, returning true if this was the case. instanceof is a binary infix operator whose left operand is an object and whose right operand is an object type. It returns true if the left operand is of the type specified by the right operand It differs from the .constructor property in that it "walks up the prototype chain." If object a is of type b, and b is an extension of c, then a instanceof b and a instanceof c both return true, whereas a.constructor === b returns true, while a.constructor === c returns false.

Inheritance by PrototypesEdit

The prototype of an object can be used to create fields and methods for an object. This prototype can be used for inheritance by assigning a new instance of the superclass to the prototype.

function CoinObject()
{
    this.value = 0; 
    this.diameter = 1;
}
 
function Penny()
{
    this.value=1;
}
Penny.prototype = new CoinObject();
 
function Nickel()
{
    this.value=5;
}
Nickel.prototype = new CoinObject();

Inheritance by functionsEdit

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To do:
Provide a recommended method for function-based inheritance - one reference is http://www.crockford.com/javascript/inheritance.html

function CoinObject()
{
    this.value = 0; 
    this.diameter = 1;
}
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Last modified on 7 August 2012, at 12:52