WEBVTT 00:01.300 --> 00:06.730 It's time to talk about one of the most fundamental aspects in JavaScript, that is variables and data 00:06.730 --> 00:10.930 types, they are a little bit different from the standard programming languages. 00:10.930 --> 00:16.840 And so I'm going to explain what variables are and what kind of data types JavaScript accepts in details 00:16.840 --> 00:17.680 step by step. 00:18.640 --> 00:20.280 So what is a variable? 00:20.620 --> 00:26.800 It's helpful to think of variables as containers, that whole information which we can use for multiple 00:26.800 --> 00:29.230 times and we can change it dynamically as well. 00:30.250 --> 00:30.730 All right. 00:31.660 --> 00:34.960 In order to declare variables, we need to write var keyword. 00:35.830 --> 00:41.500 This was the engine that it needs to reserve some memory in which to store your data later. 00:42.340 --> 00:49.090 So again, when we declare the variable JavaScript engine understands that it has to create memory space 00:49.090 --> 00:50.720 in which you can store the data. 00:51.640 --> 00:54.790 Actually, this stuff is about how JavaScript works behind the scenes. 00:55.210 --> 00:59.230 So it's the topic of another section and we will definitely discuss it deeper. 01:00.640 --> 01:04.300 Okay, after that, you should set the name to the variable. 01:05.200 --> 01:11.920 Many other programming languages which are called strongly typed languages like Java or C Sharp require 01:11.920 --> 01:16.780 you to declare not only the variable, but also the type of data that will be stored. 01:17.650 --> 01:24.040 However, JavaScript is a weekly typed language and you don't need to limit yourself to what type of 01:24.040 --> 01:25.720 data the variable can hold. 01:26.470 --> 01:32.710 It means that JavaScript engine understands itself what type of data you are storing in the variable. 01:33.740 --> 01:41.120 In this case, verbal person is not assigned by the value, it's just declared we can use a shorthand 01:41.120 --> 01:44.680 method for declaring the multiple variables in one statement. 01:45.110 --> 01:51.920 We just need to write var keyword only once, followed by names of the variables and separated them 01:51.920 --> 01:56.730 by commas that at the end of the statement we have to place semicolon. 01:57.380 --> 02:00.020 So right here, for example, first name. 02:02.180 --> 02:11.000 Last name and age in the real world, this and method is very popular and commonly used in previous 02:11.000 --> 02:15.830 video, you have already seen how to assign a value to the variable for doing that. 02:15.830 --> 02:21.950 We just need to use equal sign, which is known as assignment operator, and it doesn't mean equality 02:21.950 --> 02:22.730 as it's in math. 02:24.170 --> 02:27.090 In this case, the variable person has the value. 02:27.110 --> 02:30.610 Instructor, let's plug it in, console, right. 02:30.620 --> 02:32.270 Console the clock, Pursell. 02:36.560 --> 02:43.790 So you think the value of person variable is structured in the same way we can also use a shortened 02:43.790 --> 02:46.100 method for assigning values like this? 02:46.640 --> 02:59.270 Right, the value for first name as John, that last name as dough and age 27, in order to organize 02:59.270 --> 03:04.790 our code nicely and to make the code easier to read, we can separate them like this way. 03:06.620 --> 03:12.590 And you may have got the question about those white spaces, but I can tell you that JavaScript engine 03:12.590 --> 03:17.060 counts them as one whitespace, so that doesn't cause any errors. 03:17.600 --> 03:22.940 As we said, we can change the values of variables dynamically to understand, well, what it means. 03:22.970 --> 03:27.170 Let's assign to person different value, like, for example, teacher. 03:29.410 --> 03:33.940 And log it in council right again, cancel that log for some. 03:37.790 --> 03:42.210 So you can see that it has changed its value from instructor into teacher. 03:42.830 --> 03:49.610 And this fact also proves that JavaScript engine rates the code line by line from top to down. 03:51.140 --> 03:56.300 All right, the council is the great seal because we can work here without logging every time from the 03:56.300 --> 04:00.950 editor, we can just type here the name of the variables like first name. 04:02.100 --> 04:09.310 That press the enter and you see that he will have value, John, in the same way we can get values 04:09.330 --> 04:14.370 for other variables for last time and also for age. 04:15.240 --> 04:15.750 All right. 04:17.230 --> 04:22.350 You remember from the previous video where we were talking about Syntex parser and writing the valid 04:22.350 --> 04:22.680 code. 04:23.370 --> 04:26.100 So we need to protect some rules when we deal with variables. 04:27.240 --> 04:31.410 If you take a look on the screen, you will see on the left side the valid variable names. 04:32.280 --> 04:38.210 We are allowed to start variable names with a letter or underscore and dollar sign. 04:38.700 --> 04:43.770 And also we can use numbers in names, but we are not allowed to start the names with them. 04:45.070 --> 04:50.860 The first case is commonly used when the name includes two or more words ever, next word starts with 04:50.860 --> 04:53.980 a capital letter and it's called Camil Case Method. 04:55.380 --> 05:01.350 As for the examples on the right side, you're not allowed to use that we cannot use the space inside 05:01.350 --> 05:08.430 the name, also the minus sign because it means subtraction in JavaScript and is used in mathematical 05:08.430 --> 05:09.120 operations. 05:09.960 --> 05:16.440 We're not able to start variable names with signs except underscore and dollar sign and also with numbers. 05:18.110 --> 05:24.660 OK, in this lecture we have talked about variables, how to declare them, how to assign the values 05:24.660 --> 05:26.230 and how to choose the valid names. 05:26.790 --> 05:27.730 Let's stop here. 05:28.170 --> 05:32.190 See you in the next video where you will learn about data types in JavaScript.