Question

Probably a very basic question from a confused javascript noob…

Why do

var hasthisvalue = null;
if (hasthisvalue)
    print("hasthisvalue hs value");

and

var hasthatvalue = "";
if (hasthatvalue)
    print("hasthatvalue has value");

don’t print anything, but if I combine these two

var combined = "hasthisvalue" + "hasthatvalue";
if (combined)
    print ("combined has value");

it does?

Or more directly:

var combined = null + "";
if (combined)
    print ("combined has value");

Why does “combined” has a value if I only add two variables that don’t have values? What am I missing?

Answer 1

When you compare them separately, each converts to false in the if check. When you combine them, the null becomes the string "null", so their concatenation is the string "null", which does not convert to false