Learn JavaScript #3 | Integers, Strings, and Variables

So, a couple videos ago I had said that if we don't use quotations here it's going to think we're passing in multiple values each one as a variable. So when you write a word in JavaScript that is not in quotes, JavaScript doesn't know that it's supposed to just be a string or a sentence, for instance. So we tell it that it is by using quotations. So, we're going to be learning a bit more about variables and strings in this next line. You create a variable in JavaScript by using the keyword var, and notice how it turns blue in my editor, and I'm going to hit space and now we're going to name the variable. So, I'm going to name it welcome_message, and then you put a space and an equal sign, and you're going to assign a value to be used every time we use welcome message in our code. And so in this case it's going to say "This is a welcome message stored inside a variable." We're going to end that with a semicolon. Now, this is a string. It's going to be used as though it were text. This is not. This is going to be used as though it has a value inside of this, but this is not the value. This is called a variable. So what I'm going to do down here is I'm going to alert welcome_message, and what's going to happen here is when the page loads it's going to call the alert function and what it's going to pass into it to you know use as the content of the alert is going to be welcome message, but it's not just going to print out welcome message, is that a capital L? No, it's just how it slanted it there. It made it italicized, rather. It's not going to print out welcome message it's going to print out the value that we've assigned to that welcome message. So, it's you know you can rather than printing out if we wanted to to do this multiple times, we wouldn't want to write this out multiple times. We're just going to you know alert that multiple times. Let's save it and refresh, and as you'll see it does print out the value of the variable not the variable name. So, that's what a variable is and that's what a string is. Now, these are types. So what a type is basically what type of type is this...what type is this? So, this type is a keyword, this type is a variable, and this type is a string. Let's say we want to create a variable called age, or rather myAge. We're going to set it equal to my age which right now is 28 I believe...that sounds right. Alright, so, now notice that I did not put this into quotations, that's very important. Integers, or full numbers, do not go inside of quotations unless you want them to be a string which you can't do like math on for instance. So this is a number, it's a number. Now, a float is kind of like a number as well. So, let's go ahead and say exactAge. I'm going to set that's 28.23, sounds about right. So, what this is, is a float. And what that means is it's a floating-point number, it has a decimal in it. So if you were writing out $28 and 23 cents, for instance, it would be 28.23 not just 28. So that's how you would write it in JavaScript. This is a float, and this up here is an integer. And we're going to be discussing those more at some point, but for the most part these you can play around with these now. You can actually do math with these because they're numbers, but if we put them in quotations we wouldn't be able to do math on them. And, I'm going to show you guys what I mean right now actually. So I'm going to remove this and I'm going to print myAge plus exactAge. I'm going to save it, and now when I go back to refresh this this is going to print out 56.23 because it knows that it can do that operation on this. It can add 28 to 28.23 because they are numbers. What happens when I change both of them to strings like this by putting quotations around them and making them text instead of numbers? I'm going to refresh and it says it's 2828.23, and that's because it's just putting those two strings together as though they were this, alright. So, that's the difference between a string and an integer, well that's the main difference I guess. Another thing is that we can't add an integer to a string. You may have guessed this, and we can't add a float to a string. So I'm going to say welcome_message plus exactAge. So this should print out this is a welcome message stored inside a variable 28.23. That's what we would expect to happen. So, okay refresh. Oh, it did do that, alright. That was an integer. Okay, was it the console.log that didn't work in. So, it converts it all to a string now. That never used to be that way, at least as I'm thinking. We can also separate them by a comma here, and that leaves this as a floating point, so if you need to use that later on you can. And then we also have other types. You can use single quotes for strings as well, but we're just going to leave it at this for right now. So, you guys now know how to create variables, strings, integers, floats, and you know how to call a few functions. So, moving on we're going to be discussing more about basic types and basic things you can do with them.