In computer programming, processing data is really important. Therefore, to process data more effectively, the computer industry has made and is making lots of efforts to categorize data more effectively. So in this chapter, we are going to learn what kinds of data there are in JavaScript. And of them, we will focus on the most popular forms of data that you are probably familiar with, which are string and number. We will learn about them in detail. First, we need to understand what data type is. Let's find out what data types there are in JavaScript... by search! Type in javascript and data type. We've got various search results related to data type. Among them, let's open the page managed by Mozilla Foundation. We can learn that in JavaScript there are 6 data types and a concept called Object. You don't need to know everything on this page. For now, you can focus on number and string here. In this chapter, we are going to look into string and number,

two data types that are relatively familiar to you to understand what data type is as well as characteristics of the data types. Right-click and select Inspect. And you will see these developer tools. I selected Console. I just opened the Console on this page, but you can use Console on any page you want. Let me represent numbers here. When you represent a number, simply type it in. Sounds too obvious? But it might not necessarily be the case. You will find this out soon. So if I create an alert window and add 1 like this, what will happen? We will get this number 1 in the alert window like this. Then, what if I enter 1+1 instead? We've got 2. But it's quite a hassle to add alert every time and it's also bothersome to close the window every time. So here's an easy way for you to use it like a calculator. You can just type in 1+1 directly over here. Let me press enter. And see? We've got 2.

Right? It's just as simple as that. In the number data type, what's really important is operation. And this + - this one right here where the cursor is hovering over. The plus sign means adding the left operand to the right operand to get a value. And it's called binary operator. How it's called is not important. But FYI, among binary operators, this is specifically called arithmetic operator because it is used for arithmetic. The plus sign is one of the arithmetic operators. What other arithmetic operators are there? There are many, but let's focus on 4 fundamental arithmetic operations. 2 minus 1 equals 1, right? Minus is one of them. And 2 times 4 is 8. An asterisk (*) indicates multiplication in programming. 6 divided by 2 equals... 3. So, a slash (/) means division in programming. So far, we have learned how we can represent the number data type and looked into four arithmetic operators, which operate numbers to give a value.

Next, let's learn more about the string data type. You enclose a string in quotation marks like this. If you prefer to use a single quotation mark, you are free to do so as long as you use them as a pair. In other words, use an opening double quotation mark with a closing double quotation mark or use an opening single quotation mark with a closing single quotation mark. By the way, in the number data type, what's important is arithmetic operator. That's the most popular feature. On the other hand, in strings, there are very useful features. For example, if you want to know how many characters there are in the string, you can type in .length, and it counts the number of characters. Or it's supposed to... haha. It doesn't work if there's a typo like this. Now, it returns the result - 11 characters. So this is one of the examples. But I cannot tell you everything because there are simply too many features. Instead, let me show you how to search to find what commands you can use for strings.

javascript and string. Then we have got various search results. Among them, I'm going to open the page run by Mozilla. If you look at the left side of this web page, you will see the string.length which we just used. If you click it, there's a description that we can add .length, followed by examples showing how we can use it. The length here is called a property. But for now, it's too much for you to understand what a property is. So you can just listen and skip this part. And we can see other forms, such as method. Of them, let's have a look at some interesting examples. Here's something called toUpperCase. We can use it this way. And as you see, if you type in a string and add .toUpperCase, the result will be displayed in an uppercase. Let's do it ourselves. At the end of hello world, I'm going to add .toUpperCase. But we've got an error message. Coding an everlasting fight against typo...

Anyway, as you see, hello world, which used to be in lowercase, are now in uppercase. Exciting, isn't it? And what else? Let's have a look at this one - indexOf. To use indexOf, it says you can add the value you want to find right here. Let's do it. Over here, I'm going to type in indexOf and then add O. And press enter. We've got - 1, which means it can't find the value. But if I replace the O with the small letter o, this time we've got 4. 0 1 2 3... and on the 4th, there's the small letter o. And if I add world instead, 0 1 2 3 4 5... On the 6th location, there's the string world. And here's another example. For example, I'm typing in hello, and adding some black space. And if I press enter, the space stays intact.

But if I type in trim, the space is gone. Of course, we still don't know many things. You don't know what this period means, or what grammar are these brackets for. But what's important is getting used to it, rather than understanding it. Just try to get yourself familiar with what you've seen. For example, adding indexOf will give me this result. And later on, you will have a chance to sum up what you've learned through experience to a set of grammar rules. Until then, don't worry about your experience and lack of knowledge in grammar. Let's think about this: Is this a string or a number? Of course, it's a number data type. Then how about this? It's a string. And 1+1 equals 2. Then, what's the result of string 1 plus string 1? 11. As you see, the result can vary a lot depending on the data type. So please pay attention to use a correct data type properly. And now, let's go back to our example code.

and check whether there are strings. If you look at this section, black is enclosed in quotation marks. What that means is the black is a string, so is the white, and the black over here. The body here as well. So, we have learned about strings and numbers, and also learned that they are different data types. We also learned about data types. For the rest of data types, we will have a chance to learn them later on.

WEB2 JavaScript - 6.데이터타입 - 문자열과 숫자

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