WEBVTT 00:01.200 --> 00:06.900 In this lecture, we're going to talk about one of the most popular new features of ESX, I'm going 00:06.900 --> 00:12.810 to introduce you what area functions are, as we said, the main goal of release of ECMAScript 2015 00:12.810 --> 00:15.600 version was to minimize the amount of code. 00:16.020 --> 00:20.880 And one of the perfect examples to achieve that in Essex is to use eral functions. 00:21.900 --> 00:27.600 First of all, I would like to mention that generally arole functions do not completely replace standard 00:27.600 --> 00:30.290 functions which we're using as usually. 00:31.050 --> 00:36.450 And in order to avoid unexpected results in errors, you need to definitely understand well in which 00:36.450 --> 00:40.020 situations and in which case this is better to use function functions. 00:41.060 --> 00:47.690 Again, in this lecture, I'm going to compare our functions to standard function declarations, so 00:47.690 --> 00:50.300 I'm going to create a simple function expression. 00:50.910 --> 00:53.720 Let's create constant variable multiply. 00:54.670 --> 01:01.300 Which equals to anonymous function with two parameters, X and Y. 01:03.090 --> 01:10.020 Inside that function, let's create let's variables that which will store the multiplication of X and 01:10.020 --> 01:15.660 Y parameters and then return the value of Z. 01:16.780 --> 01:24.220 OK, let's invoke dysfunction with some arguments, right, cancel that log, multiply and place here 01:24.220 --> 01:26.740 as an arguments five and six. 01:28.380 --> 01:34.440 Revote, and we have, of course, 13, as you see, this function expression does not contain lots 01:34.440 --> 01:36.920 of characters and it's very easy to read. 01:36.930 --> 01:42.360 But thanks to general functions in Essex, we can write this function in more concise way. 01:43.020 --> 01:49.560 For that, we have to get rid of Keywood function then after parameters. 01:50.530 --> 01:57.010 We have to place erro, which actually consists of equal and greater than signs, you may be surprised 01:57.010 --> 02:02.920 how this function expression works without the keyboard function, but if we reload the page, then 02:02.920 --> 02:04.140 we will get the same results. 02:05.020 --> 02:09.250 You might think that's why do we need to replace function keyboard with that arrow? 02:09.620 --> 02:15.820 I mean that at a glance, there is not a huge difference between the amount of code in this case and 02:15.820 --> 02:22.210 in previous one, but actually using eral functions, we can transform this function into more concise 02:22.210 --> 02:22.510 form. 02:22.780 --> 02:28.020 What do we have two or more statements inside Culebra basis than in its sixth version? 02:28.030 --> 02:37.120 We have to maintain those Kolob races, but if we return here directly X multiplied to Y without that 02:37.120 --> 02:37.690 variable. 02:39.350 --> 02:46.360 Then we can remove these color braces and then remove even the written keyword. 02:48.690 --> 02:54.670 Now, we can say that this is really short and concise transformation of function expressions. 02:55.080 --> 02:56.910 This is a really great feature. 02:56.910 --> 03:02.460 But on the other hand, to read the code is a little bit hard, especially when you first introduced 03:02.460 --> 03:03.050 this feature. 03:03.540 --> 03:06.200 But I think that it's an issue of practicing. 03:07.410 --> 03:12.480 So in this case, we have two parameters here, and that's why we surround them with parentheses. 03:13.050 --> 03:20.340 But in case of one parameter, let's suppose we have only X, which then is multiplied to 10. 03:24.270 --> 03:30.180 Then we don't need to use that parenthesis anymore, reload the page and you see that it works. 03:31.650 --> 03:36.000 So, again, when we use only one parameter, we can write it without parentheses. 03:36.900 --> 03:45.780 All right, let's see what happens if we don't have parameters, let's delete X and then write five 03:45.780 --> 03:49.950 multiplied to ten and also remove this argument. 03:51.270 --> 03:51.870 Reload. 03:53.600 --> 03:59.420 And you see that we have syntax error, JavaScript engine cannot recognize what this error is here. 03:59.930 --> 04:06.680 So when we use function expressions and we don't have parameters, then we have to place your empty 04:06.680 --> 04:07.380 parentheses. 04:08.090 --> 04:09.710 So you see that it works now. 04:11.030 --> 04:11.570 OK. 04:12.540 --> 04:19.110 Let's say we want to return as a value and object, but without using return Keywood, if we simply 04:19.110 --> 04:22.050 create an object with property first name. 04:24.330 --> 04:31.620 John, then we will get in counsel undefined, so in order to avoid this unexpected value, we have 04:31.620 --> 04:36.360 just to surround this object with parentheses and that it will work. 04:37.870 --> 04:43.810 All right, one of the key points regarding Arrow functions is that we can use them only with anonymous 04:43.810 --> 04:44.440 functions. 04:45.040 --> 04:50.300 If we want to declare function statements, then we have to do it in a usual way. 04:51.490 --> 04:52.000 All right. 04:52.420 --> 04:57.540 In this lecture, we have discussed just the basic syntactic changes about functions in ethics. 04:58.150 --> 05:03.160 Let's move on to the next lecture in which I'm going to show you some more important features regarding 05:03.160 --> 05:04.000 arole functions. 05:04.930 --> 05:05.620 Let's go ahead.