var myFirstName = "Niall";
var myLastName = "Kader";
var myAge = 38;
var myDogsAge = 5;
var myBoolean = true;


alert(myFirstName + ' ' + myLastName);



alert(myFirstName + ' ' + myLastName + myAge + myDogsAge)



alert(myFirstName + ' ' + myLastName + (myAge + myDogsAge)); //notice how the parenthesis sets the order of operations



alert(myFirstName + ' ' + myBoolean);



alert(20 + 100);



alert(20 > 100);


Be careful when concatenating vars that have different data types in them.
JavaScript will try to convert data types when they get mixed together
but you don't always get what you might expect with out explicity converting with parseInt(), parseFloat(), etc.