How does JavaScript .prototype work? -

i'm not dynamic programming languages, i've written fair share of javascript code. never got head around prototype-based programming, 1 know how works?

var obj = new object(); // not functional object obj.prototype.test = function() { alert('hello?'); }; // wrong!  function myobject() {} // first class functional object myobject.prototype.test = function() { alert('ok'); } // ok 

i remember lot discussion had people while (i'm not sure i'm doing) understand it, there's no concept of class. it's object, , instances of objects clones of original, right?

but exact purpose of .prototype property in javascript? how relate instantiating objects?

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edit

these slides helped lot understand topic.

every javascript object has internal property called [[prototype]]. if property via obj.propname or obj['propname'] , object not have such property - can checked via obj.hasownproperty('propname') - runtime looks property in object referenced [[prototype]] instead. if prototype-object doesn't have such property, prototype checked in turn, walking original object's prototype-chain until match found or end reached.

some javascript implementations allow direct access [[prototype]] property, eg via non-standard property named __proto__. in general, it's possible set object's prototype during object creation: if create new object via new func(), object's [[prototype]] property set object referenced func.prototype.

this allows simulate classes in javascript, although javascript's inheritance system - have seen - prototypical, , not class-based:

just think of constructor functions classes , properties of prototype (ie of object referenced constructor function's prototype property) shared members, ie members same each instance. in class-based systems, methods implemented same way each instance, methods added prototype, whereas object's fields instance-specific , therefore added object during construction.

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