Question

In Javascript, I define global variables sld_label where label can be any string. These are initialised to objects that have a setval function. I need to check, within a function which is handed label in a string parameter called qq, whether sld_label has been defined. How do I do this without raising an error?

At the moment I have the following (which works but generates an error in Firebug) :-

function setclrques(qq,op)
{
  if (typeof(eval('sld_'+qq))=='object') eval('sld_'+qq+'.setval('+op+')');
}

Help!

Answer 1

I implemented something like this.

function Test()
{
}

Test.prototype.setval = function(options)
{
    alert(options);
}

function setclrques(qq,op)
{
    var obj = window['sld_'+qq];
    if( obj!=undefined && obj.setval!=undefined )
    {
        obj.setval(op);
    }
}

var sld_qwer = new Test();
setclrques("qwer","test!");

However I’d recommend you to consider associative array instead of separate variables for storing the objects if possible:

function Test()
{
}

Test.prototype.setval = function(options)
{
    alert(options);
}

var sld = [];
sld["qwer"] = new Test();

function setclrques(qq,op)
{
    var obj = sld[qq];
    if( obj!=undefined && obj.setval!=undefined )
    {
        obj.setval(op);
    }
}

setclrques("qwer","test!");