1 00:00:00,750 --> 00:00:05,880 All right guys are the first pattern we're going to look into is the module pattern and a slight variation 2 00:00:05,880 --> 00:00:08,550 of it called the revealing module pattern. 3 00:00:08,550 --> 00:00:15,630 Now I do want to mention that E-6 or EIAS 20:15 introduced actual modules in javascript meaning that 4 00:00:15,630 --> 00:00:22,020 we can use separate files to export modules which are just custom pieces of code and import them into 5 00:00:22,020 --> 00:00:23,160 a new file. 6 00:00:23,160 --> 00:00:25,760 However this is still not supported in browsers. 7 00:00:25,770 --> 00:00:32,910 You'll have to use a compiler like Babel along with a module loader like web pack for that to work and 8 00:00:32,910 --> 00:00:34,920 we will be getting into that later. 9 00:00:35,010 --> 00:00:40,020 But in the last five we have something called the module pattern that allows us to break up parts of 10 00:00:40,020 --> 00:00:47,940 our code into self-contained modules with private properties and methods or private variables and functions. 11 00:00:47,940 --> 00:00:55,350 So this is actually my favorite pattern and we're going to build a 12 video calorie counter application 12 00:00:55,350 --> 00:00:57,020 with it in the next section. 13 00:00:57,030 --> 00:01:03,210 So let's take a look at how the module pattern works as well as the revealing module pattern. 14 00:01:03,210 --> 00:01:09,180 So basically what we want to do where we have our index each team out here just have a heading and then 15 00:01:09,180 --> 00:01:10,310 we're connecting our app. 16 00:01:10,320 --> 00:01:14,390 J Yes but the way that the module pattern is set up. 17 00:01:14,490 --> 00:01:18,510 Let me just give you a basic structure here. 18 00:01:19,380 --> 00:01:26,940 So we have a module which is going to be in if we can if you guys remember what it is it's immediately 19 00:01:27,330 --> 00:01:32,430 invoked function expression and it runs right away. 20 00:01:32,430 --> 00:01:37,770 So we need to wrap it in parentheses to make it an expression we need to put a function in here an anonymous 21 00:01:37,770 --> 00:01:44,180 function and we need to put parentheses after it to Dick to run it. 22 00:01:44,400 --> 00:01:48,000 And then the idea of the module pattern is to declare 23 00:01:50,280 --> 00:01:59,190 private variables and functions up here and then we have a return. 24 00:01:59,190 --> 00:02:03,630 And what I mean by private meaning that we can't access it from outside the module. 25 00:02:03,840 --> 00:02:12,540 And then whenever we return this is where we declare public variables and functions. 26 00:02:12,540 --> 00:02:12,840 All right. 27 00:02:12,840 --> 00:02:17,050 So that's that's the the blueprint for the module pattern. 28 00:02:17,070 --> 00:02:23,430 Now we're going to have a pretty large project that's going to be a calorie tracker using the module 29 00:02:23,430 --> 00:02:26,570 pattern where we're going to have an item controller. 30 00:02:26,750 --> 00:02:31,560 Each module will be its own controller of an item controller that will take care of the meal items that 31 00:02:31,560 --> 00:02:39,870 we add will have a UI controller that will take care of anything to do with the UI so clicks and form 32 00:02:39,870 --> 00:02:43,010 submissions rendering stuff in the UI. 33 00:02:43,010 --> 00:02:47,880 Anything to do with that will be in the UI controller will have a storage controller that will persist 34 00:02:47,880 --> 00:02:52,950 things to local storage and then we'll have a main app controller where everything will kind of meet 35 00:02:52,980 --> 00:02:55,110 and we'll call an initialiser. 36 00:02:55,110 --> 00:03:03,090 All right so what are you going to do here is comment this out and let's create a module called UI controller. 37 00:03:03,150 --> 00:03:12,890 So UI see TRL and we're going to set that to a module modules so this will be an iffy. 38 00:03:14,340 --> 00:03:20,370 And like I said anything we we declare up here is going to be private so I'm going to create a variable 39 00:03:20,370 --> 00:03:28,620 called text and when I said that to the text of hello world and then all I want to have here is a function 40 00:03:28,620 --> 00:03:31,440 that's going to change this heading right here. 41 00:03:31,440 --> 00:03:34,950 This H-1 to whatever is in this text. 42 00:03:34,980 --> 00:03:38,000 So let's go ahead and create a variable. 43 00:03:38,080 --> 00:03:45,450 So this would be a function expression will create a variable called Change text and we'll send it to 44 00:03:45,480 --> 00:03:46,380 a function 45 00:03:49,080 --> 00:03:54,070 and let's say Konst element and let's grab that H-1. 46 00:03:54,120 --> 00:04:02,940 So document Daut let's do queries selector and we'll just grab it by the tags so H-1 and then we're 47 00:04:02,940 --> 00:04:08,950 going to say elements Daut text content and set that to text. 48 00:04:09,000 --> 00:04:15,380 Ok so we can access any any value any variables we put up here we can access from within this function. 49 00:04:15,780 --> 00:04:17,310 Now both of these are private. 50 00:04:17,310 --> 00:04:24,750 We can access these from outside of this module of the controller module we just put a comment here 51 00:04:24,870 --> 00:04:33,420 saying that this is the standard module pattern and what we want to do is return something from this 52 00:04:33,420 --> 00:04:34,250 module. 53 00:04:34,410 --> 00:04:41,230 OK so what we return is going to be public which is stuff that we can access from outside. 54 00:04:41,400 --> 00:04:54,000 So I'm going to have a function called Call change text and set that to a function and then let's run 55 00:04:54,510 --> 00:05:01,950 change text because we can access the private values the private Boll's the private functions we can 56 00:05:01,950 --> 00:05:05,550 access from within these public functions. 57 00:05:05,550 --> 00:05:10,560 All right so we'll do that and we'll also go ahead and cons. Daut log text just to show you that we 58 00:05:10,560 --> 00:05:13,100 can access that variable directly. 59 00:05:13,530 --> 00:05:26,310 OK so now outside of the module which would be down here we can say UI control or Daut call change text. 60 00:05:26,310 --> 00:05:26,670 All right. 61 00:05:26,670 --> 00:05:31,740 So go ahead and save and you can see that it actually changes to Hello World. 62 00:05:31,740 --> 00:05:36,150 It also logs hello world which is coming from right here. 63 00:05:36,270 --> 00:05:41,600 Now if I were to try to console log actual Just do it over here. 64 00:05:41,810 --> 00:05:48,630 And chrome if I were to take the UI controller and you can you'll see I can do. 65 00:05:48,630 --> 00:05:50,970 Call change tax which you just did. 66 00:05:50,970 --> 00:05:59,310 I can't however do change text if I do that it's going to see change text is not a function because 67 00:05:59,310 --> 00:06:03,060 I can't access this private function from outside. 68 00:06:03,060 --> 00:06:03,360 All right. 69 00:06:03,360 --> 00:06:06,930 We get the same error if I try it over here in fact I'll do that. 70 00:06:06,930 --> 00:06:17,560 It's a UI control word Daut change text and you see I get the same error. 71 00:06:17,710 --> 00:06:28,860 And if we try to access say UI control text we try to access this right here and save that is see that 72 00:06:31,830 --> 00:06:33,410 change sex is not a function. 73 00:06:33,450 --> 00:06:34,730 Let me just comment that. 74 00:06:35,060 --> 00:06:38,930 That's blocking and you'll see that will get undefined for that. 75 00:06:38,970 --> 00:06:41,310 This hello world is coming from this right here. 76 00:06:41,310 --> 00:06:46,530 If I were to comment this so you'll see we just get undefined. 77 00:06:46,880 --> 00:06:51,770 OK so that's that's the foundation of the module pattern we have private stuff here. 78 00:06:51,850 --> 00:06:55,270 And whatever is in this return is going to be public. 79 00:06:55,300 --> 00:07:02,200 So let's go ahead and comment this so and I'm going to give you an example of the revealing module pattern 80 00:07:03,730 --> 00:07:06,990 which is very very similar. 81 00:07:07,000 --> 00:07:15,700 The main difference is that instead of returning our own public functions like we did here you basically 82 00:07:15,700 --> 00:07:23,310 map an object literal and you map to private functions that you want to reveal. 83 00:07:23,350 --> 00:07:29,110 And that's that's why it's called the revealing pattern because you can reveal certain methods from 84 00:07:29,110 --> 00:07:30,940 your your module. 85 00:07:30,940 --> 00:07:39,820 So what we're going to do here use a different example and let's call this the item controller. 86 00:07:39,820 --> 00:07:48,850 So this would be like a databased controller and will set that to a module which is just an iffy function 87 00:07:48,850 --> 00:07:53,290 that invokes automatically. 88 00:07:53,470 --> 00:07:56,380 And let's say let data. 89 00:07:57,100 --> 00:08:01,950 And we're going to set that to an empty array so this can be thought of as as our state. 90 00:08:01,960 --> 00:08:02,320 All right. 91 00:08:02,320 --> 00:08:05,530 And then we'll create private methods here like ADD 92 00:08:08,230 --> 00:08:18,180 so will say add and I'll take an item and then we'll just take that data array and we'll push onto it 93 00:08:18,300 --> 00:08:27,090 that item and then we'll simply just do a console log and we'll say item added 94 00:08:30,170 --> 00:08:37,500 All right now a lot of times you might see an underscore with variables like this because this is a 95 00:08:37,500 --> 00:08:39,440 private variable. 96 00:08:39,780 --> 00:08:44,850 If you remember back in I think it was Section 2 when we talked about conventions for naming variables 97 00:08:45,150 --> 00:08:48,780 I told you that this is you can do this it's allowed. 98 00:08:48,900 --> 00:08:54,990 But you should only do it if it's a private variable and you won't you're only going to deal with private 99 00:08:54,990 --> 00:09:00,780 variables in more advanced stuff like this like using different patterns so that's where you might see 100 00:09:00,780 --> 00:09:01,100 that. 101 00:09:01,110 --> 00:09:01,830 I don't do that. 102 00:09:01,830 --> 00:09:05,040 I don't use the underscore but you might see that in other people's code. 103 00:09:05,190 --> 00:09:09,180 Or you may want to use it yourself. 104 00:09:09,210 --> 00:09:14,910 So let's also create a function called get and forget. 105 00:09:15,000 --> 00:09:17,580 It's going to take in an ID. 106 00:09:18,320 --> 00:09:25,380 OK so it'll take an item id and then I'm going to return the data and I'm just going to use the the 107 00:09:25,380 --> 00:09:34,710 find method here and then passing a value actually will say item and let's add that to an arrow function 108 00:09:34,740 --> 00:09:45,080 and then we'll return let's say return item Daut ID if it's equal to the ID that's passed in. 109 00:09:45,210 --> 00:09:45,510 All right. 110 00:09:45,510 --> 00:09:46,850 So those are adding getting. 111 00:09:46,860 --> 00:09:49,980 Right now these are these are completely private. 112 00:09:50,070 --> 00:09:59,400 So if we go down here and we say return and what we're going to return is an object literal here with 113 00:09:59,490 --> 00:10:08,580 at let's say ADD and set that to add and then say get set to get making those make basically revealing 114 00:10:08,580 --> 00:10:09,790 these methods. 115 00:10:09,810 --> 00:10:20,790 So then we can go down here and we can say item controller Daut add and then let's pass and here an 116 00:10:20,790 --> 00:10:33,230 object with an ID just say Id one name John and save that and we get item added. 117 00:10:33,390 --> 00:10:33,760 All right. 118 00:10:33,780 --> 00:10:44,550 And we could even go in here now and say item controller and we could do get in let's get the item with 119 00:10:44,550 --> 00:10:52,640 the idea of one and it gives us John OK and we can do the same thing over here so will say item dog 120 00:10:52,680 --> 00:11:01,020 gets the idea of one actually will need to console log that 121 00:11:06,670 --> 00:11:15,390 flips item controller OK and I could add another item here if I wanted. 122 00:11:15,430 --> 00:11:23,650 I don't know why items are people but that's fine I'll say Mark and then we'll get the item with two 123 00:11:24,370 --> 00:11:25,690 and you can see we get Mark. 124 00:11:25,690 --> 00:11:32,840 Now if I were to not have this right here if I comment that out that's going to make make this private. 125 00:11:32,890 --> 00:11:36,430 OK if we don't include it in this return it's going to be private. 126 00:11:36,430 --> 00:11:40,650 And if I save we're going to get an error saying that it's not a function. 127 00:11:40,660 --> 00:11:40,990 All right. 128 00:11:40,990 --> 00:11:46,020 So that's one of the main differences between the revealing module and the standard module pattern is 129 00:11:46,030 --> 00:11:52,480 that we're mapping or we're returning an object literal that directly reveals methods that are inside 130 00:11:52,480 --> 00:11:53,400 of the module. 131 00:11:53,500 --> 00:11:53,770 All right. 132 00:11:53,770 --> 00:11:55,910 Hopefully that makes sense. 133 00:11:56,080 --> 00:11:58,630 Now this looks cleaner. 134 00:11:58,630 --> 00:12:04,410 The revealing module pattern does look cleaner but this allows you to do more because you can. 135 00:12:04,420 --> 00:12:10,720 You know you can call change tacks but you can do other stuff as well like console log something without 136 00:12:10,720 --> 00:12:13,750 having to include it in your actual private method. 137 00:12:13,750 --> 00:12:20,000 So I mean it's all up to you what you want to use and it depends on what you're building as well. 138 00:12:20,020 --> 00:12:23,820 So you know it's all up to you. 139 00:12:23,920 --> 00:12:30,100 My job is to just introduce you to these patterns in these ways of doing things and then you know you 140 00:12:30,100 --> 00:12:32,590 make your choice on what you want to do. 141 00:12:32,590 --> 00:12:35,430 All right guys that's going to be it for this video in the next video. 142 00:12:35,430 --> 00:12:41,230 I want to talk about the singleton pattern which is actually a very another variation of the module 143 00:12:41,230 --> 00:12:48,460 pattern that uses an iffy but it has it's a little different where you can it's use to create objects 144 00:12:48,490 --> 00:12:51,680 but you can only instantiate the object once. 145 00:12:52,090 --> 00:12:54,130 So we'll get into that next.