hello

im having an issue with a couple of javascript objects which are behaving quite strangely, could someone tell me if the following is standard behaviour, and if so, how can i change it.

i have 2 Objects in my code. when a user makes changes to a form a function is called which stores all of the current form selections into Ob1, then the form selections are validated and IF the new selection is permitted and validation passes, i make Ob1=Ob2;. Otherwise Ob2 remains as it was before the function was called.

Following this function i reload all of the form selections according to the info stored in Ob2.

The problem is that as soon as i make Ob1=Ob2, subsequent changes to Ob1 affect Ob2 automatically. Is this what should be happening? If so, is there a way i can stop it?

thanks

mark m

Objects that are created from the DOM will automatically update their properties when the DOM is updated, so you would have to copy the attributes by creating a new object with properties that represent each form feature if you don't want this to happen.

Setting objB = objA only creates a copy of objA. It does not create a new instance of the object.
What you need to do is to create a new object from objA then they become separate entities.

var objB = new objA

objB then inherits all the properties and values from objA, but only at the time of instantiation, so subsequent changes to the objA will not affect objB.

So. Welcome to the wonderful world of Object Oriented Programming and Inheritance then

massive thanks to you both.

im sure there's a very good reason for this inheritance you speak of, but at the moment to me it seems like odd behaviour since all other things ive encountered in programming have worked differently.

thanks again for enlightening me.

If you really want to be confused, study the prototype property (which exists on every single JavaScript object, which is pretty much everything since everything in JavaScript is an object). Inheritance, in JavaScript, is said to be prototypal (as opposed to classical). It is the only mainstream language that uses this type of inheritance.

ive been looking at a few object tutorials and prototype has come up quite a bit, i dont understand a word of it at the moment, the only reason i began using objects as opposed to simple arrays was that JSON seemed to prefer them. Im extremely confused

technically, an associative array is an object. Arrays and objects can both be expressed like this:

var myArray = [];
myArray["myKey"] = "Hello World!";
var myObject = {};
myObject.myProperty = "Hello World!";

alert(myArray["myKey"]);
alert(myObject["myProperty"]);

both will alert "Hello World!". Note that I alerted the myObject.myProperty as if it were an array. This is perfectly valid, though it is not often used.

yeah i get the basics now, its when people start mentioning classes and things that i lose track. Ive not yet come into a situation where i havnt been able to do what i need with the basic knowledge i have, and therefore have not begun to confuse myself with proper programming practises. my code is cumbersome and probably doesnt follow the standards, but i usually get it to work as i want and you cant teach an old dog new tricks.