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These are the user uploaded subtitles that are being translated: 1 1 00:00:01,310 --> 00:00:04,240 Welcome back to your first coding challenge 2 2 00:00:04,240 --> 00:00:05,523 of this section. 3 3 00:00:07,170 --> 00:00:10,950 So now it's time to finally put everything that you learned 4 4 00:00:10,950 --> 00:00:14,400 in the section so far into practice. 5 5 00:00:14,400 --> 00:00:15,720 So in this section, 6 6 00:00:15,720 --> 00:00:18,490 I want you to use a Constructor Function 7 7 00:00:18,490 --> 00:00:22,550 in order to implement a very simple car all right? 8 8 00:00:22,550 --> 00:00:26,470 So for this purpose, a car has just a make 9 9 00:00:26,470 --> 00:00:28,530 and a speed property, 10 10 00:00:28,530 --> 00:00:32,080 and the speed is simply the current speed of the car 11 11 00:00:32,080 --> 00:00:35,000 measured in kilometers per hour, 12 12 00:00:35,000 --> 00:00:38,600 then I want you to implement an accelerate method 13 13 00:00:38,600 --> 00:00:41,720 that will increase the car speed by 10, 14 14 00:00:41,720 --> 00:00:45,370 and it would also log the new speed to the console, 15 15 00:00:45,370 --> 00:00:48,100 then another method called brake, 16 16 00:00:48,100 --> 00:00:50,730 which will then decrease the speed 17 17 00:00:50,730 --> 00:00:53,840 but only by five all right? 18 18 00:00:53,840 --> 00:00:58,040 And finally I want you to use this test data down here 19 19 00:00:58,040 --> 00:01:00,470 to implement these two cars. 20 20 00:01:00,470 --> 00:01:03,390 So basically to create two car objects 21 21 00:01:03,390 --> 00:01:06,640 and then experiment with calling the two methods 22 22 00:01:06,640 --> 00:01:10,080 that we just created on each of the objects. 23 23 00:01:10,080 --> 00:01:12,770 And of course you should use all the knowledge 24 24 00:01:12,770 --> 00:01:15,990 from the previous lectures to doing this. 25 25 00:01:15,990 --> 00:01:18,980 So I hope that this is a fun challenge 26 26 00:01:18,980 --> 00:01:20,870 that's not too hard. 27 27 00:01:20,870 --> 00:01:22,860 So take all the time that you need 28 28 00:01:22,860 --> 00:01:26,263 and I see you back here when you're ready with my solution. 29 29 00:01:29,770 --> 00:01:34,610 All right so hopefully you did that successfully, 30 30 00:01:34,610 --> 00:01:36,620 so let's get started here, 31 31 00:01:36,620 --> 00:01:41,050 so we create the Constructor Function for car 32 32 00:01:41,050 --> 00:01:43,490 and one more time with a capital C 33 33 00:01:44,350 --> 00:01:49,110 and then we want each car object to have a make and a speed 34 34 00:01:49,110 --> 00:01:51,090 and so that's the arguments 35 35 00:01:51,090 --> 00:01:53,780 that we're gonna pass into this function. 36 36 00:01:53,780 --> 00:01:56,940 And then just as before under this property, 37 37 00:01:56,940 --> 00:02:00,970 we will set the make to the make that we receive 38 38 00:02:00,970 --> 00:02:01,950 and the speed, 39 39 00:02:01,950 --> 00:02:04,083 to the speed that we receive as well. 40 40 00:02:05,060 --> 00:02:08,493 And so this is basically always gonna work the same way. 41 41 00:02:09,930 --> 00:02:11,160 So as I mentioned, 42 42 00:02:11,160 --> 00:02:14,750 this is a pattern that developers came up with 43 43 00:02:14,750 --> 00:02:16,920 and so now we just simply follow this 44 44 00:02:16,920 --> 00:02:20,200 like a recipe all right? 45 45 00:02:20,200 --> 00:02:23,903 And with this, we can actually already create our two cars, 46 46 00:02:25,180 --> 00:02:30,180 so let's say the BMW is a new car 47 47 00:02:30,290 --> 00:02:33,760 and so remember this new operator here 48 48 00:02:33,760 --> 00:02:36,193 is what's gonna enable all of this to work. 49 49 00:02:37,330 --> 00:02:40,150 And so here the make is of course BMW 50 50 00:02:40,150 --> 00:02:43,820 and the speed is 120 kilometers per hour, 51 51 00:02:43,820 --> 00:02:48,820 which for my American friends is 75 miles per hour 52 52 00:02:49,300 --> 00:02:50,790 I believe 53 53 00:02:50,790 --> 00:02:53,223 so the next one is gonna be the Mercedes. 54 54 00:02:55,800 --> 00:02:57,060 So that's new car 55 55 00:02:58,200 --> 00:03:02,120 and at speed, 95 kilometers per hour okay? 56 56 00:03:05,900 --> 00:03:07,600 So let's just take a look 57 57 00:03:08,970 --> 00:03:09,803 and so yeah, 58 58 00:03:09,803 --> 00:03:12,820 that appears to be working just fine. 59 59 00:03:12,820 --> 00:03:16,730 And so now let's implement our two methods here, 60 60 00:03:16,730 --> 00:03:19,030 so accelerate and brake 61 61 00:03:19,030 --> 00:03:22,833 and of course we are not going to add the method right here. 62 62 00:03:23,750 --> 00:03:26,950 So we will not do this .accelerate 63 63 00:03:26,950 --> 00:03:29,400 because as we just learned before, 64 64 00:03:29,400 --> 00:03:31,760 that would be terrible for performance, 65 65 00:03:31,760 --> 00:03:34,773 especially if we had many, many car objects. 66 66 00:03:35,610 --> 00:03:38,725 So instead we will of course make use 67 67 00:03:38,725 --> 00:03:41,466 of prototypal inheritance. 68 68 00:03:41,466 --> 00:03:44,550 So we take the prototype property of car 69 69 00:03:44,550 --> 00:03:49,550 and to that, we add the accelerate property accelerate 70 70 00:03:52,380 --> 00:03:53,620 that's correct 71 71 00:03:53,620 --> 00:03:57,690 and we make it a method by passing in a function 72 72 00:03:58,610 --> 00:04:01,693 or actually by specifying a function here. 73 73 00:04:03,280 --> 00:04:04,690 So once again, 74 74 00:04:04,690 --> 00:04:06,810 we can use the This keyword in here 75 75 00:04:06,810 --> 00:04:09,360 because that is simply gonna be the object 76 76 00:04:09,360 --> 00:04:12,100 on which the method will be called 77 77 00:04:12,100 --> 00:04:15,080 and so that object will have the speed property 78 78 00:04:15,080 --> 00:04:18,313 and so here we can then increase that by 10. 79 79 00:04:21,470 --> 00:04:24,750 And then we can also log that to the console 80 80 00:04:25,730 --> 00:04:28,403 and we can even make use of course of the make. 81 81 00:04:29,870 --> 00:04:33,220 So this one wasn't specified in the text, 82 82 00:04:33,220 --> 00:04:35,420 but we can log a nice string, like this 83 83 00:04:36,640 --> 00:04:38,130 is going 84 84 00:04:38,130 --> 00:04:42,360 at this.speed 85 85 00:04:43,750 --> 00:04:46,010 and then kilometers per hour 86 86 00:04:46,010 --> 00:04:47,223 but again this part, 87 87 00:04:48,073 --> 00:04:50,223 you wouldn't have to implement like this. 88 88 00:04:51,350 --> 00:04:53,000 And now let's just take this here 89 89 00:04:54,280 --> 00:04:57,553 for the brake because it's gonna be pretty similar, 90 90 00:04:58,630 --> 00:04:59,720 so brake, 91 91 00:04:59,720 --> 00:05:01,710 and all we do then is to 92 92 00:05:01,710 --> 00:05:06,710 decrease the speed by five all right? 93 93 00:05:07,240 --> 00:05:11,053 And now let's just call this on the BMW a couple of times, 94 94 00:05:12,020 --> 00:05:15,223 so bmw.accelerate, 95 95 00:05:16,200 --> 00:05:17,863 and let's do that three times. 96 96 00:05:18,950 --> 00:05:20,380 And so after three times, 97 97 00:05:20,380 --> 00:05:25,230 the BMW is going at 150 kilometers per hour, 98 98 00:05:25,230 --> 00:05:28,320 so apparently that works just fine. 99 99 00:05:28,320 --> 00:05:30,370 Let's just add a brake here in the middle 100 100 00:05:34,890 --> 00:05:37,930 and so now we reduce the speed a little bit 101 101 00:05:37,930 --> 00:05:42,200 and then back up to 145 now okay? 102 102 00:05:42,200 --> 00:05:44,200 And that's actually it, 103 103 00:05:44,200 --> 00:05:47,230 that's all we had to do in this challenge, 104 104 00:05:47,230 --> 00:05:48,800 and maybe with this example, 105 105 00:05:48,800 --> 00:05:51,100 you can start to see the advantages 106 106 00:05:51,100 --> 00:05:54,520 of object oriented programming in action. 107 107 00:05:54,520 --> 00:05:56,910 So all the advantages that we talked about 108 108 00:05:56,910 --> 00:05:59,990 right in the first lecture of the section, 109 109 00:05:59,990 --> 00:06:02,380 and essentially the part where we learned 110 110 00:06:02,380 --> 00:06:04,590 that in object oriented programming, 111 111 00:06:04,590 --> 00:06:09,350 we pack both the functionality and the data into objects. 112 112 00:06:09,350 --> 00:06:12,160 And so that's exactly what we have here, 113 113 00:06:12,160 --> 00:06:14,170 so each of these objects, 114 114 00:06:14,170 --> 00:06:19,170 so BMW and Mercedes contains the state of the car, 115 115 00:06:19,260 --> 00:06:22,350 so the current speed and the make, 116 116 00:06:22,350 --> 00:06:24,780 and it also contains the functionality 117 117 00:06:24,780 --> 00:06:27,420 to manipulate its own data, 118 118 00:06:27,420 --> 00:06:31,010 so the accelerate and brake methods in this case 119 119 00:06:31,010 --> 00:06:34,650 are able to manipulate the speed, right? 120 120 00:06:34,650 --> 00:06:36,160 And at the same time, 121 121 00:06:36,160 --> 00:06:39,560 these two methods also form the public interface 122 122 00:06:39,560 --> 00:06:42,210 of this object, right? 123 123 00:06:42,210 --> 00:06:44,300 So right now the rest of our code 124 124 00:06:44,300 --> 00:06:47,010 can interact with these objects 125 125 00:06:47,010 --> 00:06:50,740 by calling the brake and the accelerate methods. 126 126 00:06:50,740 --> 00:06:52,473 Now in this case, of course, 127 127 00:06:52,473 --> 00:06:55,730 this is just a very small and isolated example, 128 128 00:06:55,730 --> 00:06:59,430 so it can still be hard to see the advantages of this, 129 129 00:06:59,430 --> 00:07:01,920 but maybe you can take a minute or two 130 130 00:07:01,920 --> 00:07:04,180 and compare this style of coding 131 131 00:07:04,180 --> 00:07:07,090 with the code that we have written up until this point 132 132 00:07:07,090 --> 00:07:08,180 in the course. 133 133 00:07:08,180 --> 00:07:11,090 All right, so at some point you will see 134 134 00:07:11,090 --> 00:07:14,650 that this is really a completely different way of thinking 135 135 00:07:14,650 --> 00:07:16,200 about our code, 136 136 00:07:16,200 --> 00:07:19,010 but anyway that's it for this challenge. 137 137 00:07:19,010 --> 00:07:20,060 In the next video, 138 138 00:07:20,060 --> 00:07:23,290 we are gonna talk about ESX classes, 139 139 00:07:23,290 --> 00:07:24,993 so I hope to see you there soon. 11707