How did it go? 0:00 If you didn't get it to work, you can watch my solution 0:01 compared to what you wrote and then try to recreate it yourself. 0:04 Also, keep in mind, 0:07 there are usually many different ways to solve a programming challenge. 0:08 Your solution may be different than mine and still work, that's fine. 0:12 So the first thing that I'll do is I'll move the declarations for the num2 and 0:15 message variables to the top of the math.js file. 0:20 I'll also remove the var keywords from down below. 0:23 This practice session requires that you use a conditional statement. 0:30 But where should you put it? 0:33 Let's look at the requirements again. 0:35 I'm supposed to check the values of the inputs, are they numbers or not? 0:39 So I can put the conditional statement right after I collect input from the user. 0:43 So I start with the if clause, followed by a condition in parentheses, 0:52 and braces to mark the opening and closing of the conditional. 0:56 Anything I add in here will run only if number 2 is equal to 0. 1:00 I'll add an alert Message. 1:05 Let's see how this works, I'll save and preview the file. 1:10 Type a number for the first input, and 0 for the second. 1:19 Excellent, here's the alert. 1:23 Uh-oh, unfortunately, it still prints to the page, 1:26 that's because the rest of the program is outside of the conditional statement. 1:29 We need to add an else clause to stop the programming from generating and 1:34 writing this message. 1:37 I'll add an else clause and another set of brackets. 1:39 Okay, I'll save the file and preview again. 1:57 Great, I get the alert message, but nothing is printed to the doc, 2:05 that's perfect. 2:08 But I also want to check that both inputs are numbers. 2:09 I can add a branch to this conditional statement. 2:13 I'll do that using an else if clause. 2:16 To check to see if a variable holds a number, 2:29 you can use the is not a number method. 2:31 So I'll first check to see if the num1 variable is a number. 2:34 Inside these brackets, I'll add the alert message that appears if the user types 2:37 in text in the prompt dialogue. 2:41 But we also need to check the second number. 2:44 One way you could do this is adding another else if clause to test 2:47 the second number. 2:50 But that would be extra programming that's just not necessary. 2:51 Another way to do it is add two pipe characters, 2:54 followed by a second condition. 2:57 The pipe characters indicate that either one or 3:00 the other of the test have to be true. 3:03 In other words, if either number one is not a number or 3:05 number two is not a number, we should alert the user. 3:09 At this point, we have conditional statements with three branches. 3:12 The first two test for errors and the last writes a message. 3:16 Let's check it out. 3:19 I'll leave the first input blank and then type hello in the second, excellent. 3:25 And when I reload it and use numbers, it works. 3:32 I hope you're able to complete this practice successfully. 3:36 If not, why not start over and 3:39 try to write the program without looking at my version. 3:40 Have fun with JavaScript, and see you again soon. 3:43