Get name of object instance's variable?

[WA]

Hi there:
Is it possible to probe the name of the variable assigned to an object instance in JavaScript? For example:

function house(){
}

var bobhouse=new house()
if (instancename=="bobhouse")
 //do something

In other words, can I do some sort of string comparison on the variable name "bobname", so I know it's actually called "bobname"? I feel I'm asking how to have a variable recognize itself as a variable.

[chump2877]

outside of making the variable name a property of the object, I can;t think of a better way:

function house(id)
{
    this.id = id;
}

var bobhouse = new house("bobhouse")

if (bobhouse.id == "bobhouse")
{
    alert("it works");
}

[WA]

Ah thanks, but I was looking for a way to dynamically detect the variable instance's name, instead of manually remembering it.

[chump2877]

Maybe you can alter the prototype of a function object to get it to do what you want to? That might be similar to what I did. I don't think there's a "built-in" way for JS to do what you want.

[rnd me]

functions have a .name property, but onlew function objects.

you will have to sweep window to find the name of your non-function variable.

the example below works for firefox, not sure about other browsers.

function obSub(ob) {var r = [];var i = 0;for (var z in ob) {
if (ob.hasOwnProperty(z)) {r[i++] = z;}}return r;}

function getVarName(variable){
   return obSub(window).map(function(a){ 
           if( window[a] === variable ){return a} }).sort()[0]
}




function House(){  }
var tre = new House()
alert( getVarName(tre) )

[WA]

Thanks md_me. Haven't tested your code in IE yet, but if that's what it requires in terms of complexity, I think I'll just choose an alternate approach to my problem. Thx though.

[chump2877]

Originally Posted by rnd me

functions have a .name property, but onlew function objects.

you will have to sweep window to find the name of your non-function variable.

the example below works for firefox, not sure about other browsers.

function obSub(ob) {var r = [];var i = 0;for (var z in ob) {
if (ob.hasOwnProperty(z)) {r[i++] = z;}}return r;}

function getVarName(variable){
   return obSub(window).map(function(a){ 
           if( window[a] === variable ){return a} }).sort()[0]
}




function House(){  }
var tre = new House()
alert( getVarName(tre) )

I get the code here, but my question to WA is: If you're dealing with a bunch of "house" object instances, isn't manually creating a "name" property for the "house" function object easier?

[rnd me]

Originally Posted by chump2877

I get the code here, but my question to WA is: If you're dealing with a bunch of "house" object instances, isn't manually creating a "name" property for the "house" function object easier?

you cannot alter the name property of a function object.

at least not in firefox:

function test(){
  return true 
}

alert(test.name) // shows test
test.name = "newname"
alert(test.name) // shows test

if there is not a name used (anonymous), as in :

var test = function (){
  return true 
}


alert(test.name) // shows ""
test.name = "newname"
alert(test.name) // shows ""

it still doesnt work...

OP:


you might consider declaring your own top level object like App ={} at the top of your script, and assign properties to it as you write your other code.

ex: App.goodNumbers=[1,2,3,4]

later : alert(App.goodNumbers);

it is easier and safer to iterate that App object than the window object, and can be done across browsers relatively simply.

[chump2877]

you cannot alter the name property of a function object.

I'm sorry, I didn;t mean literally name the property "name"...any property named something else (other than "name") that serves the purpose of identifying a given function object instance, i meant...

Per the example in my first post to this thread...

[Trinithis]

Originally Posted by WA

In other words, can I do some sort of string comparison on the variable name "bobname", so I know it's actually called "bobname"? I feel I'm asking how to have a variable recognize itself as a variable.

What would happen if there are multiple variables referencing the same object?

If anything, unless I'm horribly wrong, I would suspect that there is a much better way of solving a problem than this. Variables shouldn't need to know about other variables . . . that's your job (from a lexical standpoint). Variables just need to know values.

[WA]

Variables shouldn't need to know about other variables . . . that's your job (from a lexical standpoint). Variables just need to know values.

Perhaps, and it's really more of a curiosity than necessarily to do this for me at this point. Broadening the question though, is there a way for a variable to know what it itself is called? Something like:

var x=5
if (nameOf(x)=="x")
 //do something

[D-motivatie]

Originally Posted by WA

Hi there:
Is it possible to probe the name of the variable assigned to an object instance in JavaScript? For example:

function house(){
}

var bobhouse=new house()
if (instancename=="bobhouse")
 //do something

In other words, can I do some sort of string comparison on the variable name "bobname", so I know it's actually called "bobname"? I feel I'm asking how to have a variable recognize itself as a variable.

You could try something like this:

function house(instanceName)
{
	// move this to global scope
	eval(instanceName + " = this;");

	// remember instance name
	this.instanceName = instanceName;

	//retreive instance name
	this.getInstanceName = function ()
	{
		return this.instanceName;
	}

	//default property
	this.toString = function ()
	{
		return this.getInstanceName();
	}
}

//create instances with name bobhouse and jefhouse
new house("bobhouse");
new house("jefhouse");

//should alert "bobhouse";
alert( bobhouse.getInstanceName() );

//should alert "jefhouse" (default property toString());
alert( jefhouse );

regards

Jeffrey van der Stad - D-motivatie

[D-motivatie]

Originally Posted by WA

Hi there:
Is it possible to probe the name of the variable assigned to an object instance in JavaScript? For example:

function house(){
}

var bobhouse=new house()
if (instancename=="bobhouse")
 //do something

In other words, can I do some sort of string comparison on the variable name "bobname", so I know it's actually called "bobname"? I feel I'm asking how to have a variable recognize itself as a variable.

After playing around, you could also do this

// JSON house: (JavaScript Object Notation)
var house = {
	
	// method to create global instance:
	create: function ( instanceName )
	{
		eval( instanceName + " = new house.object('" + instanceName + "')" );
	},

	// this is the actual created global object
	object: function ( instanceName ) 
	{
		//remember instance name
		this.instanceName = instanceName;

		//default property
		this.toString = function ()
		{
			return this.instanceName;
		}
	}
}

//create instances
house.create("bobhouse");
house.create("jefhouse");

//alert instance names
alert( bobhouse ); //alert ("bobhouse");
alert( jefhouse ); //alert ("jefhouse");

//alert instance names (using property instanceName)
alert( bobhouse.instanceName ); //alert ("bobhouse");
alert( jefhouse.instanceName ); //alert ("jefhouse");

it's more complex, but you can do so much more with complexity

Regards

Jeffrey van der Stad - D-motivatie

[md9547]

I know this is an old thread but as it's top on google for the question I'll post the solution I just found to this: http://www.liam-galvin.co.uk/2010/11...n-object/#read