Validating Email Addresses

validate.js

function validateEmailAddress(s) {
 var  atSym = "@", dot = ".";
 if (s.indexOf(atSym) === -1 || s.indexOf(" ") !== -1 || s.indexOf(atSym) > s.lastIndexOf(dot) || s.length - s.lastIndexOf(atSym) < 3 || s.lastIndexOf(atSym) + 1 === s.lastIndexOf(dot) || s.length - s.lastIndexOf(dot) <== 2 ) return false;
        else return true;
}

A nice trick: the structure

if (someComplexCondition) {
    return true;
} else {
    return false;
}

Can be improved to:

return someComplexCondition;

Or, if you really want to ensure that the type returned is a boolean, then you can use:

return !!someComplexCondition;