Can I break a try - catch in JS without throwing exception?

You can label a block and break from it using the break label syntax

as per your edit, finally is still executed

foo = function(){
    var bar = Math.random() > .5;
    omgalabel: try {
        if( bar ) break omgalabel;
        console.log( bar );
        // code 
    }
    catch( e ){
        //  This code should not execute if !!bar 
    }
    finally {
        // Code that executes no matter what
        console.log( true );
    }
}

var error;
var bar = Math.random() > .5;
try{
   if(bar){throw new Error('#!@$');} // Break this try, even though there is no exception here.
   //  This code should not execute if !!bar 
   alert( bar );
   }
catch(e){
   if(e.stack.indexOf('#!@$')==-1){error=e;}
   }
finally{
   if(error){
       //an actual error happened
       }
   else{
       // Code that executes if !!bar
       alert( true );
       }
   }

you can throw a error inside try catch and detect the string of the error stack to see if it was an expected throw or an actual error you didn't expect

foo = function(){

    var bar = Math.random() > .5;
    if( ! bar ) {
        try{
            //  This code should not execute if !!bar 
            alert( bar );
        }
        catch( e ){
            console.error(e);
        }
    }

    // Code that executes no matter what
    alert( true );
}

foo();

Why don't you check the boolean before you enter the try…catch?