Introduction to JavaScript Conditionals. If Statements. An if statement is a specific block of code that will execute when a given condition is true. To explain this, I'm gonna write if parentheses condition, curly brackets statement. So how does this work? If this condition is true, meaning that it passes the statement, which is the block of code inside of the curly brackets, gets executed. If the condition is false, it fails, and nothing happens.

And what are conditions? Conditions can be logical operators or comparison operators, or a combination of both. Anything that returns a boolean value, including variables that are set to boolean values and using the code that's currently on the screen, I'm gonna begin with a comparison operator. First, I'm gonna clear this out and I'm gonna make the condition number one is greater than number two. So this function is gonna take two values represented by the parameters number one and number two, and compare them. And depending on the outcome of that comparison, some specific code is gonna execute. And inside of the curly brackets, I'm gonna set message equal to number one is greater than number two.

After the if statement, I'm gonna return the message that way the current value of message is gonna be made available when this function is executed. At the bottom, I'm gonna console log the compared numbers function, passing in the arguments of both the number one and number two variables that are at the top. And in the console, we can see the message number one is greater than number two, demonstrating that the current value of message was set because the comparison operator evaluated to true. If the condition evaluated to false failing, the statement would have never executed and message would have been left undefined.

Now, what if we wanted to check for another condition, if the first condition is false? We can chain additional checks by using the else/if statement. Else/if number one, triple equals number two, and inside of the curly brackets, I'm gonna set message equal to both numbers are equal. And now I'm gonna set the value of the number two variable to 15 to ensure that this condition triggers. I'm gonna execute this again and in the console, we can see the message that both numbers are equal.

So if the first condition fails, as long as there is a else if statement, the interpreter will continue to check for any additional conditions that may pass and then execute the statement for that passing condition. And you can chain multiple else/if statements, one after another, for each condition you wish to check. The only rule is that the first condition must be wrapped with the eight if statement.

Now, what if all conditions fail? That's where the else statement is used. So now I'm gonna type else, currently brackets, message equal number two is greater than number one. Know that with the else statement, there is no condition and it completely relies on the failure of all previous conditions. And I'm gonna set number two to 20. And when I execute this again, we can see in the console that number two is greater than number one. And that's it. Thanks for watching at Cloud Academy.