Passing object in javascript function

Question

Say I already have many objects, like obj1, obj2, .....obj30.....

Now I am trying to write a function like this:

function blar(N){
 do something to objN
} 
blar('4');

So far it seems that the only way to do it is

function blar(thisObj){
 do something to thisObj
}
blar(obj4);

I wonder what is the right way to pass the N such that the function can use that N value to process objN.

Hope I make myself clear.

PS: I even try something like blar(obj+N) but apparently it's wrong too, as the system tries to find obj, which doesn't exist.

• Jhourlad Estrella: Object... Number. Let me try that again: Object, Number...

Answer 1

Use square bracket notation.

window['obj' + N];

This depends on them dangling off the window object and not being nicely scoped though.

... but if you have a bunch of objects, which are identified by being the same except for a number, then you should probably be storing them in an array in the first place. Then you would just:

myArray[N];

• Vern: Oh, why I never think of array. Thanks for the great tip!

Answer 2

Use eval:

function blar(N) {
 var obj = eval("obj"+N);
}

Or, if you can put those objects into an object, you can use []

function blar(N) {
 var obj = tracker["obj" + N];
}

Answer 3

It's pretty simple:

function blar(objectNo) {
 var obj = eval('obj' + objectNo);
 alert(obj);
}

To give you some keywords for talking with others about this: what you want to do is to access an object by its name, in the current scope.

But note that the following doesn't work:

function main() {
 var a = 1, b = 2, c = 3;
 blar('a'); // doesn't work
 doSomething(eval('a')); // works
}

This is because the variable a is only visible in the main function, but not in blar. That is, the eval must be called in a scope where the variable is visible.