Javascript's inheritance is prototype based, so you extend the prototypes of objects such as Date, Math, and even your own custom ones.
Date.prototype.lol = function() {
alert('hi');
};
( new Date ).lol() // alert message
In the snippet above, I define a method for all Date objects ( already existing ones and all new ones ).
extend
is usually a high level function that copies the prototype of a new subclass that you want to extend from the base class.
So you can do something like:
extend( Fighter, Human )
And the Fighter
constructor/object will inherit the prototype of Human
, so if you define methods such as live
and die
on Human
then Fighter
will also inherit those.
Updated Clarification:
"high level function" meaning .extend isn't built-in but often provided by a library such as jQuery or Prototype.
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