Advanced conditions and logic

When we work with conditional statements and logic operators it's often necessary to string multiple different conditions together, and for that we have two logic operators called AND and OR. These allow us to do things like say, if "a" equals "b" and "c" equals "d" or if "a" equals "b" or "c" equals "d". For AND statements we use two ampersands and for OR statements we use two vertical lines or pipes. When using logical AND and logical OR it's important to understand what logical AND and logical OR actually mean because it's not what it sounds like.

This makes a lot more sense if we use a venn diagram. In logic, AND means both conditions must be true for the whole statement to be true. That makes sense. OR means either the first statement or the second statement or both statements are true. Commonly, when we speak in human language we would expect that OR means either "a" or "b" but not both, but in computer logic, it actually means either "a" or "b" or both. This leads to a third condition where either "a" or "b" are true but not both.

For this we need a conditional logical test called XOR, but XOR doesn't exist in JavaScript. So, we need to create it manually. Let's say we have two conditions: "a" equals "b" and "c" equals "d" and we want to do something if either one of them is true but not both. To get that to work we have to nest a conditional statement inside a conditional statement. So at the bottom here, what we're saying is, if "a" equals "b" or "c" equals "d", so that would be either or, and "a" equals "b" is not equal to "c" equals "d".

So this gives us either "a" or "b" but not "a" and "b". Here you see how conditionals can be very powerful once you get the hang of how the logic works. When you start looking at code on the web, you'll quickly discover there's a shorthand for these IF/ELSE statements we talked about previously, and at first glance it looks pretty weird. This is the Ternary Operator. Ternary because it has three pieces to it. Take this as an example: "a" equals "b", question mark, console log, match, colon, console log, no match.

Okay. So, what on Earth is going on here? Let's look at the original code. If "a" equals "b" then console log match, else console log no match. This is easy enough to understand. And the Ternary Operator says the exact same thing. It literally says, if condition "a" equals "b" is true, then do one thing, else do something else. The Ternary Operator makes this into a single line of code for us where it says the condition, question mark, the true statement, colon, the false statement.

So, if "a" equals "b" is true, then console log match. Otherwise, console log no match. IF/ELSE statements are used all the time in JavaScript and this Ternary Operator takes up a lot less space than writing out the full statement. Now that you know how it works, you'll be able to recognize it and use it yourself to make your code more nimble. Just keep in mind what I previously mentioned; your code needs to make sense to humans. Ternary Operators are not immediately obvious, so use them with care and add comments when you do so to explain what's going on.