Javascript: What's more efficient, IF block or TRY/CATCH?

Question

I'd love some other opinions on what's more efficient in this code. Basically in the following code, there's a setInterval loop and I need 4 requirements to be true before the code runs in the loop. So in v.1 I wrote an if statement checking all 4. Worked fine.

Then I switched to just using try/catch, with the code I want to execute sitting in try{}. The logic was that during each loop, an exception would be generated but suppressed for each invalid condition. On the final loop where all conditions are true, the code executes and clears the interval.

Either works. I like the try/catch method because there's less conditional code that I need to write and worry about breaking. But I'm worried that try/catch is really inefficient, especially in a setInterval() loop hitting at 100ms. What are some opinions of other bright minds here on SO?

Try/Catch

var intvar = setInterval(function(){
try{    
    clearInterval(intvar);

    jQuery('#'+nav[pageid].t1+'>a').replaceWith(jQuery('<span>'+jQuery('#'+nav[pageid].t1+'>a').text()+'</span>'));

    //set display classes for nav
    jQuery('#'+nav[pageid].t1).addClass('selected').find('#'+nav[pageid].t2).addClass('subselect'); //topnav
    jQuery('#'+nav[pageid].t3).addClass('selected').find('#'+nav[pageid].t4).addClass('subselect'); //leftnav
}catch(err){}
},100);

IF Block

var intvar = setInterval(function(){

if(typeof jQuery == 'function' && typeof nav == 'object' && typeof pageid != 'undefined' && typeof document.getElementById('leftnav') == 'object'){
    clearInterval(intvar);
    jQuery('#'+nav[pageid].t1+'>a').replaceWith(jQuery('<span>'+jQuery('#'+nav[pageid].t1+'>a').text()+'</span>'));

    //set display classes for nav
    jQuery('#'+nav[pageid].t1).addClass('selected').find('#'+nav[pageid].t2).addClass('subselect'); //topnav
    jQuery('#'+nav[pageid].t3).addClass('selected').find('#'+nav[pageid].t4).addClass('subselect'); //leftnav
}

},100);

Answer 1

Exceptions should be used for exceptional circumstances (i.e. things that you don't expect to happen normally). You should not, in general, use exceptions to catch something that you can test for with an if statement.

Also, from what I understand, exceptions are much more expensive than if statements.

Answer 2

Use the if statement. I don't know what the overhead is for a TRY/CATCH, but I suspect it's far greater than evaluating a boolean expression. To hit the TRY/CATCH you will have to: execute a statement, generate an error [with that associated overhead], log the error (presumably), made a stacktrace(presumably), and moved back into the code. Additionally, if you have to debug code near those lines the real error could get obfuscated with what you are TRY/CATCHing.

Furthermore, it's a misuse of TRY/CATCH and can make your code that much harder to read. Suppose you do this for longer or more obfuscated cases? Where might your catch end up?

This is referred to as Exception handling

EDIT: As commented below, you only take the runtime performance hit if you actually cause an exception.