WEBVTT 00:01.530 --> 00:06.810 As we said previously, JavaScript is an object based programming language, and therefore in JavaScript, 00:06.810 --> 00:08.550 almost everything is an object. 00:08.970 --> 00:14.160 Object is a little bit complex data type, and we want to refer to it yet because the whole section 00:14.160 --> 00:15.930 is waiting for you regarding objects. 00:16.680 --> 00:19.330 So we have just said that almost everything is an object. 00:19.350 --> 00:24.690 It means that there is something that is not an object in JavaScript and those are primitives. 00:25.660 --> 00:36.430 JavaScript provides five types of primitive data string, no boolean undefined and no all right strengths 00:36.430 --> 00:39.140 are used for storing and manipulating text. 00:39.520 --> 00:44.290 Let's create variable and assign to its value as John. 00:45.240 --> 00:46.410 Is an instructor. 00:48.840 --> 00:55.350 You tell JavaScript that text is to be treated as text and not as code, simply by enclosing it with 00:55.350 --> 00:58.290 the single quotes, let's log it in council. 00:59.790 --> 01:01.110 I'd consider it like string. 01:03.520 --> 01:09.490 So here we have our string, John is an instructor, instead of single quotes, we can use double quotes. 01:12.110 --> 01:14.400 You see that we have the same results. 01:15.050 --> 01:18.170 They work in the same way, but there is one important issue to note. 01:18.470 --> 01:20.850 The number of calls must always to be matched. 01:21.320 --> 01:26.210 It means that if something starts with double quotes, then must be and with double quotes as well. 01:26.750 --> 01:28.390 And the same for single quotes. 01:28.400 --> 01:31.400 If not, then the string value would be invalid. 01:32.370 --> 01:36.240 So you see that we got syntax error, which tells us that the value is invalid. 01:37.380 --> 01:43.260 And the last thing that I want to show you regarding strength is that if we want to surround one of 01:43.260 --> 01:48.480 the words by quotes, for example, instructor, we have to protect the following group. 01:48.750 --> 01:55.170 If the itself is surrounded by the double quotes, then we have to use single quotes with instructor. 01:57.220 --> 01:59.800 So you see that instructor is in quotes. 02:01.140 --> 02:08.520 OK, now let's see what happens if we don't protect this rule right here, double quotes reload and 02:08.520 --> 02:10.740 we have, again, an error. 02:12.070 --> 02:18.400 All right, let's see what has happened here, JavaScript engine rates, the code from left to right. 02:19.240 --> 02:22.770 It has found the beginning of the string value with double quotes. 02:23.260 --> 02:30.010 So also expect to see adding double quotes and when it finds that counts, that this piece of code is 02:30.010 --> 02:30.430 correct. 02:31.000 --> 02:33.400 But what it sees next is invalid. 02:33.790 --> 02:35.230 Therefore, we get an error. 02:36.880 --> 02:37.360 All right. 02:37.780 --> 02:39.220 Let's move on to the numbers. 02:39.700 --> 02:41.820 JavaScript has only one type of number. 02:42.310 --> 02:46.810 Unlike like many other programming languages, JavaScript doesn't define different types of numbers, 02:46.810 --> 02:54.360 like integers, short, long, floating port and etc. Numbers can be written with or without decimals. 02:54.670 --> 03:04.600 So let's create variable and call it number equals to twenty seven, then luggage in council. 03:08.800 --> 03:15.230 So we have here 27 and also you notice that the color is different from strong values. 03:15.250 --> 03:16.190 It's kind of blue. 03:16.720 --> 03:18.940 We can write numbers with decimals, as we said. 03:19.420 --> 03:19.690 Right. 03:19.720 --> 03:21.790 For example, point twenty three. 03:24.720 --> 03:30.240 One thing to note regarding numbers is that if we write it within quotes, then the JavaScript engine 03:30.240 --> 03:33.870 will understand that the type of value is stirring and not the number. 03:34.290 --> 03:37.710 And it's actually the important thing because it may cause unexpected results. 03:37.710 --> 03:39.110 And you will see that later. 03:39.840 --> 03:43.150 You said that in console, nothing is changed till we have the same number. 03:43.500 --> 03:46.200 The only thing that was changed is the color of the output. 03:46.590 --> 03:51.270 As we said, numbers are always shown in blue and the color of the string is great. 03:52.550 --> 03:58.910 All right, the next primitive data type is Bulleit, which has two possible values, true or false? 03:59.120 --> 04:02.680 The idea of true and false is fundamental in computer programming. 04:03.140 --> 04:07.970 The purpose of pulling data and javascript is just the same as in the world outside programming. 04:08.300 --> 04:14.420 It enables you to answer questions and make decisions based on the answer, mostly boolean data types 04:14.420 --> 04:16.040 that are used in conditional statements. 04:16.520 --> 04:20.480 And just for demonstration purposes, I would like to show you this example. 04:20.960 --> 04:22.610 Create variables, number one. 04:24.080 --> 04:24.960 Equals to five. 04:24.980 --> 04:27.660 And number two equals the ten. 04:28.580 --> 04:33.950 Let's compare these numbers and counsel writes, No one is less than number two. 04:35.770 --> 04:40.930 And he said that we have true because the statement is actually true, five is less than 10. 04:41.320 --> 04:45.550 If we were right, the opposite number one is greater than number two. 04:47.730 --> 04:51.300 Then the result will be false, and I'm sure you understand why. 04:51.870 --> 04:55.350 All right, let's move on to the new variable and. 04:56.560 --> 04:58.900 Then luggage in council. 05:01.600 --> 05:08.950 And see what happens, you see that we have undefined now let's remove this line of code and reload 05:08.950 --> 05:09.690 the page again. 05:10.360 --> 05:14.620 You see that we got an error which tells us that A is not defined. 05:15.200 --> 05:18.820 So what is the difference between undefined and is not defined? 05:19.270 --> 05:26.200 In first case, when we got undefined means that Variable A is created and JavaScript engine has reserved 05:26.200 --> 05:27.310 the memory space for it. 05:27.880 --> 05:34.060 But because of that, the variable is not assigned by the value JavaScript engine automatically assigns 05:34.060 --> 05:40.060 to it undefined, which is the special value, and also it belongs to primitive data type. 05:41.000 --> 05:45.620 So, again, if the variable is declared and is not assigned by the value, it's undefined. 05:46.920 --> 05:52.980 The second case in which we have got a is not defined means that variable itself doesn't exist. 05:53.580 --> 05:57.810 In other words, JavaScript engine could not find the variable in its memory. 05:59.420 --> 06:06.560 All right, let's talk about now, as we saw in previous example, undefined means a variable that has 06:06.560 --> 06:12.770 been declared but has not yet been assigned a value now is an assignment value. 06:13.770 --> 06:16.200 The right for A equals to null. 06:17.220 --> 06:24.030 It can be assigned to the variable as a representation of no value, so the variable whose value is 06:24.030 --> 06:31.530 undefined has never been initialized and the variable whose value is now was explicitly given a value 06:31.530 --> 06:37.050 of null, which means that the variable was explicitly set to have no value. 06:38.020 --> 06:44.280 In other words, NUL is nothing, and it's supposed to be something that doesn't exist. 06:46.030 --> 06:51.130 So, again, Undefined is automatically assigned by JavaScript engine one, the variable does not have 06:51.130 --> 06:57.790 value and we assign now to the variable in order to represent that this variable doesn't have the value. 06:59.230 --> 06:59.910 Makes sense. 07:01.390 --> 07:07.830 OK, it may be a little bit strange and confusing, but I think I made it clear for you. 07:08.320 --> 07:11.710 All right, in this lecture we have discussed briefly primitive data types. 07:12.220 --> 07:13.530 See you in the next video. 07:13.570 --> 07:14.320 Let's go ahead.