Javascript: Instance name in a class method
Question
<html>
<body>
<div id="output"></div>
<script>
function jExgTrend(){
}
jExgTrend.prototype.Start = function(text)
{
//this must return Instance name : "TestObj"
var InstanceName = "TestObj";
document.getElementById("output").innerHTML = "<a href=\"javascript:"+InstanceName+".Notify('"+text+"');\">"+text+"</a>";
}
jExgTrend.prototype.Notify = function(msg)
{
alert(msg);
}
var TestObj = new jExgTrend();
TestObj.Start("Text of the link");
</script>
</body>
</html>
How can I do something like this ? the method "Start" should return the name of the Instance of the class.
The problem is stupid I know :-(
2 answers
solution1
0 2014-01-25 13:28:06
You can't. You can specify a name at instantiation though:
function JExgTrend(name){ this.name = name || 'no name specified'; }
JExgTrend.prototype.Start = function () {
alert(this.name);
}
var testObj = new JExgTrend('testObj');
var otherTestObj = new JExgTrend('otherTestObj');
var anon = new JExgTrend;
testObj.Start(); //=> testObj
otherTestObj.Start(); //=> otherTestObj
anon.Start(); //=> no name specified
A somewhat exotic alternative: you could program the constructor like this:
function JExgTrend(name,scope) {
name = name || ( Math.floor( 10000+Math.random()*100000000000) ).toString(16);
if (!(this instanceof JExgTrend)) {
return new JExgTrend(name,scope);
}
this.name = name;
if (!JExgTrend.prototype.myname) {
JExgTrend.prototype.myname = function(){ console.log(this.name); };
}
return (scope || window)[this.name] = this;
}
And then assign objects like this:
jExgTrend.call(null, 'testObj');
testObj.myname(); //=> testObj
Try fiddling around @ this jsFiddle
solution2
0 2014-01-25 14:57:31
Maybe what you really need is an id, not a name.
Providing an id is something you can easily add with a method that you can add to Object's prototype or just to the class(es) that interest you :
var idGetter = (function() {
var currentId = 0;
return function() {
// 1. replace 'id' with a readonly property
// that will return id for this object
var thisId = currentId ;
Object.defineProperty( this, 'id',
{ get : function () { return thisId; } } ) ;
// 2. for the first run of id, return object id
return currentId++;
}
}());
Object.defineProperty( Object.prototype, 'id', { get : idGetter } );
small example of use :
var someObject = {};
console.log(someObject.id); // outputs 0
var someObject2 = {};
console.log(someObject2.id); // outputs 1
Notice that Object.defineProperty defaults to a non-enumerable property, so your objects won't get 'polluted' by this property (when using for..in for instance).
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