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These are the user uploaded subtitles that are being translated: 1 1 00:00:01,290 --> 00:00:03,750 Let's keep exploring objects 2 2 00:00:03,750 --> 00:00:07,473 and this lecture will bring us to object methods. 3 3 00:00:08,950 --> 00:00:11,900 So we learned that objects just like a race 4 4 00:00:11,900 --> 00:00:14,230 can hold different types of data. 5 5 00:00:14,230 --> 00:00:16,220 And they can hold even a race, 6 6 00:00:16,220 --> 00:00:20,400 and in fact, they could even hold objects inside objects. 7 7 00:00:20,400 --> 00:00:23,340 But now we can take it even further. 8 8 00:00:23,340 --> 00:00:25,600 And for that, remember how I said 9 9 00:00:25,600 --> 00:00:29,630 that functions are really just another type of value. 10 10 00:00:29,630 --> 00:00:31,950 And if a function is just a value 11 11 00:00:31,950 --> 00:00:35,370 then that means that we can create a key value pair 12 12 00:00:35,370 --> 00:00:37,820 in which the value is a function. 13 13 00:00:37,820 --> 00:00:40,660 And that then means that we can in fact, 14 14 00:00:40,660 --> 00:00:43,280 add functions to objects. 15 15 00:00:43,280 --> 00:00:45,750 And so let's now see how. 16 16 00:00:45,750 --> 00:00:49,030 And once more, I will get back this object here 17 17 00:00:50,010 --> 00:00:55,010 but we will change it up a little bit this time around. 18 18 00:00:55,020 --> 00:00:59,387 So here let's simplify and just put the birthYear. 19 19 00:01:00,540 --> 00:01:02,293 So just 1991. 20 20 00:01:03,150 --> 00:01:07,007 And I also want to add a Boolean here, hasDriversLicense. 21 21 00:01:10,760 --> 00:01:14,010 Just to show you that we can hold all kinds 22 22 00:01:14,010 --> 00:01:17,650 of different data types in one object. 23 23 00:01:17,650 --> 00:01:22,650 But now let's also add a function here as a key value pair. 24 24 00:01:22,780 --> 00:01:27,420 So to do that, all we have to do is to add another key here. 25 25 00:01:27,420 --> 00:01:29,970 And the function that we want to add is again, 26 26 00:01:29,970 --> 00:01:32,500 the calcAge function. 27 27 00:01:32,500 --> 00:01:35,600 So that's one of the favorites, as you can see, 28 28 00:01:35,600 --> 00:01:38,560 but it is because it's a very simple calculation 29 29 00:01:38,560 --> 00:01:41,010 that we can do with the birth year. 30 30 00:01:41,010 --> 00:01:43,870 So to do that, let's simply add the name 31 31 00:01:43,870 --> 00:01:47,060 basically off the function here as a key. 32 32 00:01:47,060 --> 00:01:48,770 So as a property, 33 33 00:01:48,770 --> 00:01:53,330 so calcAge and then the colon, and now here 34 34 00:01:53,330 --> 00:01:56,970 we simply specify the function as an expression 35 35 00:01:56,970 --> 00:02:00,327 and that works because the expression produces the value. 36 36 00:02:00,327 --> 00:02:02,423 And so we can just do this, 37 37 00:02:03,850 --> 00:02:06,810 so function, and just like before , 38 38 00:02:06,810 --> 00:02:08,430 we pass in the birth year 39 39 00:02:10,800 --> 00:02:15,800 and we return 2037 minus the birth year that was passed in. 40 40 00:02:19,410 --> 00:02:24,410 So this is pretty similar to simply writing this, right? 41 41 00:02:24,690 --> 00:02:27,110 So a regular function expression. 42 42 00:02:27,110 --> 00:02:30,283 So const calcAge like this, 43 43 00:02:30,283 --> 00:02:32,680 this is how we used to do it before. 44 44 00:02:32,680 --> 00:02:34,920 And so you see that this is pretty similar. 45 45 00:02:34,920 --> 00:02:36,880 The difference is just in the syntax 46 46 00:02:36,880 --> 00:02:41,070 because now calcAge is not a regular variable like here, 47 47 00:02:41,070 --> 00:02:43,970 but it's a property of the Jonas object. 48 48 00:02:43,970 --> 00:02:46,020 And so therefore we use the colon here 49 49 00:02:46,020 --> 00:02:48,720 but the rest here is exactly the same. 50 50 00:02:48,720 --> 00:02:50,800 And so that's why it was very important 51 51 00:02:50,800 --> 00:02:54,870 that you understood what a function expression actually is 52 52 00:02:54,870 --> 00:02:57,150 because here we need to function expression 53 53 00:02:57,150 --> 00:02:59,230 to create this method. 54 54 00:02:59,230 --> 00:03:02,210 And that's what this function is called. 55 55 00:03:02,210 --> 00:03:04,040 So any function that is attached 56 56 00:03:04,040 --> 00:03:06,643 to an object is called a method. 57 57 00:03:07,940 --> 00:03:10,750 So of course we could have not used 58 58 00:03:10,750 --> 00:03:12,790 a function declaration here. 59 59 00:03:12,790 --> 00:03:14,223 So something like this, 60 60 00:03:15,060 --> 00:03:20,060 so function calcAge, for example, that would not work, 61 61 00:03:20,830 --> 00:03:23,610 we would certainly get an error here. 62 62 00:03:23,610 --> 00:03:26,090 So unexpected token function, 63 63 00:03:26,090 --> 00:03:27,940 because this is a declaration. 64 64 00:03:27,940 --> 00:03:29,620 And so it doesn't work here, 65 65 00:03:29,620 --> 00:03:31,880 here, we need an expression. 66 66 00:03:31,880 --> 00:03:34,530 And so this will work indeed. 67 67 00:03:34,530 --> 00:03:36,870 Okay? Does this make sense? 68 68 00:03:36,870 --> 00:03:41,200 So if you can think of functions as simply being values 69 69 00:03:41,200 --> 00:03:46,010 then you can see that a method is actually also a property. 70 70 00:03:46,010 --> 00:03:47,920 It just happens to be a property 71 71 00:03:47,920 --> 00:03:50,280 that holds a function value. 72 72 00:03:50,280 --> 00:03:52,820 So here we have a string value, 73 73 00:03:52,820 --> 00:03:55,210 here we have an array value, 74 74 00:03:55,210 --> 00:03:56,937 here we have a Boolean value, 75 75 00:03:56,937 --> 00:03:58,693 and here we have a function value. 76 76 00:04:00,200 --> 00:04:01,640 All right. 77 77 00:04:01,640 --> 00:04:04,740 So, I hope that's logical. 78 78 00:04:04,740 --> 00:04:08,120 And now just like we can access any other property, 79 79 00:04:08,120 --> 00:04:12,143 we can also access the calcAge property or method. 80 80 00:04:13,410 --> 00:04:18,410 So jonas.calcAge and so calcAge is now the function value, 81 81 00:04:19,520 --> 00:04:22,680 and just like any other function in order to call it, 82 82 00:04:22,680 --> 00:04:24,800 we use the parenthesis. 83 83 00:04:24,800 --> 00:04:27,860 And now we can pass in the year here. 84 84 00:04:27,860 --> 00:04:29,960 And so that should then calculate our age. 85 85 00:04:31,550 --> 00:04:36,223 And let's just unlock this result to the console here, 86 86 00:04:38,980 --> 00:04:40,763 just to see if everything works. 87 87 00:04:41,950 --> 00:04:44,280 And it does indeed. 88 88 00:04:44,280 --> 00:04:48,640 Okay. And you could also have access 89 89 00:04:48,640 --> 00:04:51,683 to this method using the bracket notation, 90 90 00:04:52,730 --> 00:04:57,080 because again, it's just as if it was a normal property 91 91 00:04:57,950 --> 00:05:01,180 and the brackets would actually be necessary here 92 92 00:05:01,180 --> 00:05:03,930 so that this then here is the function 93 93 00:05:03,930 --> 00:05:06,923 and then we call the function using the parenthesis. 94 94 00:05:08,080 --> 00:05:09,293 So let's try that. 95 95 00:05:10,720 --> 00:05:13,683 And, yeah, here this needs to be a string. 96 96 00:05:16,350 --> 00:05:19,140 So like I showed you in the last lecture, 97 97 00:05:19,140 --> 00:05:22,560 and now here we get 46 as well. 98 98 00:05:22,560 --> 00:05:26,060 Okay. So just like I showed you in the last video 99 99 00:05:26,060 --> 00:05:28,380 with the operator proceedings table, 100 100 00:05:28,380 --> 00:05:30,360 the first thing that happens here, 101 101 00:05:30,360 --> 00:05:33,720 is that jonas.calcAge is computed. 102 102 00:05:33,720 --> 00:05:36,320 And so this here will become the function value. 103 103 00:05:36,320 --> 00:05:38,210 And then with the parenthesis, 104 104 00:05:38,210 --> 00:05:42,567 we call that function value here and passed in 1991. 105 105 00:05:42,567 --> 00:05:44,290 And the same thing here, 106 106 00:05:44,290 --> 00:05:48,110 so here we access the property calcAge using the brackets 107 107 00:05:48,110 --> 00:05:51,040 and then this here will basically be replaced 108 108 00:05:51,040 --> 00:05:52,187 with the function, 109 109 00:05:52,187 --> 00:05:57,123 and then we call the function right here, just like before. 110 110 00:05:58,840 --> 00:06:01,720 All right, now you might have noticed 111 111 00:06:01,720 --> 00:06:05,090 that the birth year 1991, 112 112 00:06:05,090 --> 00:06:07,840 that we passed here as an argument to the method 113 113 00:06:07,840 --> 00:06:09,880 is actually already defined 114 114 00:06:09,880 --> 00:06:14,400 in the Jonas object itself up here, right? 115 115 00:06:14,400 --> 00:06:18,180 So we already have this information in the Jonas object. 116 116 00:06:18,180 --> 00:06:22,840 And so writing the same number here and here is not ideal 117 117 00:06:22,840 --> 00:06:26,510 because we might make a mistake and pass in the wrong year. 118 118 00:06:26,510 --> 00:06:28,510 For example, right here. 119 119 00:06:28,510 --> 00:06:31,290 So Jonas' birth year is 91 120 120 00:06:31,290 --> 00:06:35,570 but here, we could, for some reason accidentally do 92 121 121 00:06:35,570 --> 00:06:37,180 and then it would be wrong. 122 122 00:06:37,180 --> 00:06:40,280 And even if we do not make any mistake, 123 123 00:06:40,280 --> 00:06:42,130 this is still not ideal 124 124 00:06:42,130 --> 00:06:45,090 because we are not keeping the code dry. 125 125 00:06:45,090 --> 00:06:49,170 So we're violating the don't repeat yourself principle. 126 126 00:06:49,170 --> 00:06:51,680 So if we know the birth year of Jonas, 127 127 00:06:51,680 --> 00:06:54,320 it would only be written in one place, 128 128 00:06:54,320 --> 00:06:55,970 not in multiple places, 129 129 00:06:55,970 --> 00:06:57,490 because if that might change, 130 130 00:06:57,490 --> 00:06:59,440 then we have to change it everywhere. 131 131 00:06:59,440 --> 00:07:03,290 That's always the philosophy that we need to keep in mind. 132 132 00:07:03,290 --> 00:07:07,650 So what if we could actually access this birth year property 133 133 00:07:07,650 --> 00:07:10,190 directly from the Jonas object 134 134 00:07:10,190 --> 00:07:12,890 instead of having to pass it in? 135 135 00:07:12,890 --> 00:07:16,370 Well, it turns out that we actually can, 136 136 00:07:16,370 --> 00:07:18,500 and that's because in every method, 137 137 00:07:18,500 --> 00:07:20,810 JavaScript gives us access 138 138 00:07:20,810 --> 00:07:24,110 to a special variable called this. 139 139 00:07:24,110 --> 00:07:28,230 And so what we can do now is in this calcAge function, 140 140 00:07:28,230 --> 00:07:30,210 we can read the birth year directly 141 141 00:07:30,210 --> 00:07:33,940 from this object itself without having to pass it in 142 142 00:07:33,940 --> 00:07:36,993 as a parameter here into this function. 143 143 00:07:38,130 --> 00:07:42,680 Alright, so let me copy this and comment this one out 144 144 00:07:42,680 --> 00:07:46,560 just so that we keep a record of what we did 145 145 00:07:46,560 --> 00:07:48,683 but this here will be the new version. 146 146 00:07:50,360 --> 00:07:53,900 So now we no longer need this parameter 147 147 00:07:53,900 --> 00:07:58,370 and we will read the birth year directly from the object. 148 148 00:07:58,370 --> 00:08:02,290 And for that again, we will use the this keyword. 149 149 00:08:02,290 --> 00:08:03,930 So the this key word 150 150 00:08:03,930 --> 00:08:08,190 or the this variable is basically equal to the object 151 151 00:08:08,190 --> 00:08:10,930 on which the method is called, 152 152 00:08:10,930 --> 00:08:12,260 or in other words, 153 153 00:08:12,260 --> 00:08:15,750 it is equal to the object calling the method. 154 154 00:08:15,750 --> 00:08:18,103 So, let's see who is calling the method. 155 155 00:08:19,260 --> 00:08:22,518 So down here, here is calcAge, 156 156 00:08:22,518 --> 00:08:26,620 and the object that is calling the method is Jonas, 157 157 00:08:26,620 --> 00:08:28,960 because that's where the dot is. 158 158 00:08:28,960 --> 00:08:30,650 And let's forget about this one, 159 159 00:08:30,650 --> 00:08:32,860 actually comment it out here. 160 160 00:08:32,860 --> 00:08:34,310 And so again 161 161 00:08:34,310 --> 00:08:38,970 the object that is calling the calcAge method here is Jonas. 162 162 00:08:38,970 --> 00:08:42,130 And so that means that inside this method 163 163 00:08:42,130 --> 00:08:47,130 the this variable or the this keyword will point to Jonas. 164 164 00:08:47,360 --> 00:08:51,370 And so let me just write this.birthYear here 165 165 00:08:51,370 --> 00:08:54,723 and then I can explain it even a little bit better. 166 166 00:08:55,580 --> 00:09:00,010 So, here we don't need to pass the 1991 here 167 167 00:09:00,940 --> 00:09:05,260 and I will run this now and we still get the correct result. 168 168 00:09:05,260 --> 00:09:07,140 So, great. 169 169 00:09:07,140 --> 00:09:09,593 And to make this even more clear here, 170 170 00:09:11,090 --> 00:09:14,563 let's also log this to the console, 171 171 00:09:17,660 --> 00:09:21,860 and indeed, this is the whole Jonas object. 172 172 00:09:21,860 --> 00:09:25,030 And so again, that's because the Jonas object 173 173 00:09:25,030 --> 00:09:27,950 is the one who is calling this method, 174 174 00:09:27,950 --> 00:09:29,920 so this function, 175 175 00:09:29,920 --> 00:09:33,290 see here, it's jonas.calcAge 176 176 00:09:33,290 --> 00:09:35,940 and so whatever appears before the dot 177 177 00:09:35,940 --> 00:09:37,920 is the one who is calling the method. 178 178 00:09:37,920 --> 00:09:40,200 And so therefore, in the method, 179 179 00:09:40,200 --> 00:09:43,280 this points to Jonas now, 180 180 00:09:43,280 --> 00:09:45,430 and if this points to Jonas, 181 181 00:09:45,430 --> 00:09:48,420 then this.birthYear is of course 182 182 00:09:48,420 --> 00:09:51,520 this value that we have right here. 183 183 00:09:51,520 --> 00:09:52,370 Great. 184 184 00:09:52,370 --> 00:09:54,260 So you see that the this keyword 185 185 00:09:54,260 --> 00:09:56,870 is something really, really useful 186 186 00:09:56,870 --> 00:09:59,670 and we will learn even more about the this keyword 187 187 00:09:59,670 --> 00:10:02,680 in greater detail in a later section. 188 188 00:10:02,680 --> 00:10:06,380 For now, I just wanted to introduce you to this concept 189 189 00:10:06,380 --> 00:10:09,760 and I noticed can be a bit confusing. 190 190 00:10:09,760 --> 00:10:12,540 So really make sure to maybe pause the video 191 191 00:10:12,540 --> 00:10:16,120 and really analyze what's happening here. 192 192 00:10:16,120 --> 00:10:18,090 Maybe you can even rewind a little bit 193 193 00:10:18,090 --> 00:10:20,100 and hear my explanation again, 194 194 00:10:20,100 --> 00:10:22,210 that might be useful too. 195 195 00:10:22,210 --> 00:10:25,380 Now you might argue that maybe we don't even need 196 196 00:10:25,380 --> 00:10:27,360 this confusing this keywords. 197 197 00:10:27,360 --> 00:10:31,363 Why not just do jonas.birthYear, here instead? 198 198 00:10:32,300 --> 00:10:35,520 Well, because that would actually still violate 199 199 00:10:35,520 --> 00:10:38,320 the don't repeat yourself principle. 200 200 00:10:38,320 --> 00:10:40,830 It would work just the same here now, 201 201 00:10:40,830 --> 00:10:41,930 but then let's say 202 202 00:10:41,930 --> 00:10:44,690 that we need to change the name of the object. 203 203 00:10:44,690 --> 00:10:47,150 So we change it here to Jonas2 204 204 00:10:47,150 --> 00:10:49,580 and then we call Jonas2 down here, 205 205 00:10:49,580 --> 00:10:52,683 and then the code will no longer automatically work, 206 206 00:10:53,630 --> 00:10:57,010 because now Jonas is not defined of course. 207 207 00:10:57,010 --> 00:10:59,540 And so we would have to keep that in mind 208 208 00:10:59,540 --> 00:11:02,870 and then come here and manually change this as well, 209 209 00:11:02,870 --> 00:11:05,780 while if we had the this keyword, 210 210 00:11:05,780 --> 00:11:07,910 then everything will keep working 211 211 00:11:07,910 --> 00:11:09,980 without us having to change it there, 212 212 00:11:09,980 --> 00:11:13,490 because now this will simply point to Jonas2, 213 213 00:11:13,490 --> 00:11:16,320 because that is the object calling the method. 214 214 00:11:16,320 --> 00:11:19,540 And so therefore it's always a good idea 215 215 00:11:19,540 --> 00:11:22,090 to reference the object itself 216 216 00:11:22,090 --> 00:11:24,553 and not hard-code the name of the object. 217 217 00:11:25,920 --> 00:11:30,920 So let's put it back to Jonas and yeah, much better. 218 218 00:11:33,130 --> 00:11:35,170 So this works great already, 219 219 00:11:35,170 --> 00:11:36,340 and we're really going 220 220 00:11:36,340 --> 00:11:39,450 into some more advanced territory here. 221 221 00:11:39,450 --> 00:11:41,330 So I hope you're still following me 222 222 00:11:41,330 --> 00:11:44,610 and you're still making sense of everything. 223 223 00:11:44,610 --> 00:11:48,320 However, we can actually even take this a little bit further 224 224 00:11:49,230 --> 00:11:53,000 but don't worry, it's not going to get a lot more confusing, 225 225 00:11:53,000 --> 00:11:55,560 just a small variation of this, 226 226 00:11:55,560 --> 00:11:57,850 because let's say that we need to access 227 227 00:11:57,850 --> 00:12:01,383 the age multiple times throughout our program. 228 228 00:12:02,390 --> 00:12:06,723 So that would be like calling this a couple of times. 229 229 00:12:07,940 --> 00:12:10,700 So let's say in three places of our application, 230 230 00:12:10,700 --> 00:12:12,690 we need to access the age, 231 231 00:12:12,690 --> 00:12:15,103 and so, of course this will work, 232 232 00:12:16,510 --> 00:12:18,260 and indeed it does. 233 233 00:12:18,260 --> 00:12:21,350 And it always locks the Jonas object 234 234 00:12:21,350 --> 00:12:22,950 because we still have this here. 235 235 00:12:24,280 --> 00:12:26,963 So this makes it a bit easier to view. 236 236 00:12:27,860 --> 00:12:29,380 And so what happens here 237 237 00:12:29,380 --> 00:12:33,360 is that a function will get called a total of four times. 238 238 00:12:33,360 --> 00:12:37,730 And so this computation here will be done four times. 239 239 00:12:37,730 --> 00:12:39,870 And in this case that's not a big deal 240 240 00:12:39,870 --> 00:12:42,830 but it might be a like a heavier computation 241 241 00:12:42,830 --> 00:12:45,160 that actually takes some more time, 242 242 00:12:45,160 --> 00:12:49,560 and so it would be a bad practice to do this multiple times. 243 243 00:12:49,560 --> 00:12:53,300 Instead, what we can do is to just calculate the age once, 244 244 00:12:53,300 --> 00:12:55,610 then store it in the object, 245 245 00:12:55,610 --> 00:12:58,050 and then when we need it at a later point, 246 246 00:12:58,050 --> 00:13:00,090 we can then just retrieve the age 247 247 00:13:00,090 --> 00:13:02,900 as a property from the object. 248 248 00:13:02,900 --> 00:13:05,213 So, I hope you're following me here. 249 249 00:13:07,170 --> 00:13:10,090 So I will again copy this and comment it out 250 250 00:13:10,090 --> 00:13:14,790 so that we keep all the three versions that we did here. 251 251 00:13:14,790 --> 00:13:16,770 So, what I was trying to say 252 252 00:13:16,770 --> 00:13:19,780 is that we can now use the this keyword 253 253 00:13:19,780 --> 00:13:22,023 also to store a new property. 254 254 00:13:22,860 --> 00:13:27,860 So, we can say this.age is equal to this here. 255 255 00:13:31,694 --> 00:13:33,490 So we calculate the age, 256 256 00:13:33,490 --> 00:13:37,280 and then we create a new property on the current object. 257 257 00:13:37,280 --> 00:13:40,450 So in this case, on the Jonas object, 258 258 00:13:40,450 --> 00:13:43,830 and remember that we can use the dot notation like this 259 259 00:13:43,830 --> 00:13:46,320 to create new properties. 260 260 00:13:46,320 --> 00:13:48,723 So we did that in a previous lecture as well. 261 261 00:13:51,130 --> 00:13:53,030 Where was that? 262 262 00:13:53,030 --> 00:13:54,180 Yeah, right here. 263 263 00:13:54,180 --> 00:13:56,600 So here we created jonas.location 264 264 00:13:56,600 --> 00:13:58,290 and set it to Portugal. 265 265 00:13:58,290 --> 00:14:02,430 And so here we are essentially creating jonas.age 266 266 00:14:02,430 --> 00:14:06,360 and setting it to this age that we just calculated. 267 267 00:14:06,360 --> 00:14:09,930 And then we can simply return this age. 268 268 00:14:09,930 --> 00:14:13,150 And of course we don't even need to return anything 269 269 00:14:13,150 --> 00:14:14,580 if we didn't want to. 270 270 00:14:14,580 --> 00:14:17,720 We could make this method only calculate the age 271 271 00:14:17,720 --> 00:14:19,550 but not even return it, 272 272 00:14:19,550 --> 00:14:21,160 but I think it's a good practice 273 273 00:14:21,160 --> 00:14:22,973 to actually also return it. 274 274 00:14:23,992 --> 00:14:26,650 And so now here we can replace the function call 275 275 00:14:26,650 --> 00:14:28,620 with simply a request 276 276 00:14:28,620 --> 00:14:31,000 for the age property, 277 277 00:14:31,000 --> 00:14:33,810 and notice this trick that I did here again 278 278 00:14:33,810 --> 00:14:35,920 with the command D, right, 279 279 00:14:35,920 --> 00:14:38,150 So this gives me multiple cursors 280 280 00:14:38,150 --> 00:14:40,270 and then I can do one operation 281 281 00:14:40,270 --> 00:14:42,830 in multiple places at the same time. 282 282 00:14:42,830 --> 00:14:44,570 So that's a really handy shortcut. 283 283 00:14:44,570 --> 00:14:48,000 So, again, command D, or control D 284 284 00:14:48,000 --> 00:14:52,433 and in the menu bar that means add next occurrence. 285 285 00:14:53,780 --> 00:14:57,053 So let's test this and the results should be the same, 286 286 00:14:58,410 --> 00:15:02,940 and it is, but we only needed to calculate the age once 287 287 00:15:02,940 --> 00:15:04,060 then from here, 288 288 00:15:04,060 --> 00:15:05,833 we simply retrieve the property 289 289 00:15:05,833 --> 00:15:08,470 that we had already calculated before. 290 290 00:15:08,470 --> 00:15:11,973 And so this is the most efficient solution let's say. 291 291 00:15:13,130 --> 00:15:15,880 All right, and now I actually have another, 292 292 00:15:15,880 --> 00:15:17,680 a small challenge for you 293 293 00:15:17,680 --> 00:15:20,260 that you can do just in this video. 294 294 00:15:20,260 --> 00:15:24,302 So I want you to write a method called getSummary 295 295 00:15:24,302 --> 00:15:26,720 and this method should return a string 296 296 00:15:26,720 --> 00:15:30,640 which should kind of summarize the data about Jonas, 297 297 00:15:30,640 --> 00:15:33,130 or, of course, any other person data 298 298 00:15:33,130 --> 00:15:34,583 that you might have used. 299 299 00:15:36,340 --> 00:15:37,423 For example, 300 300 00:15:38,760 --> 00:15:39,593 let me again, 301 301 00:15:41,090 --> 00:15:43,550 actually we can get rid of this. 302 302 00:15:43,550 --> 00:15:46,370 So let me write Challenge here again 303 303 00:15:46,370 --> 00:15:48,193 and then do an example string. 304 304 00:15:49,850 --> 00:15:52,400 So I want you to write for example this, 305 305 00:15:52,400 --> 00:15:57,400 Jonas is a 46 year old teacher. 306 306 00:16:01,010 --> 00:16:03,710 And we now could actually add all the data here 307 307 00:16:03,710 --> 00:16:04,800 to the string, 308 308 00:16:04,800 --> 00:16:07,150 but that would be too much work 309 309 00:16:07,150 --> 00:16:08,670 and I'm a bit lazy now. 310 310 00:16:08,670 --> 00:16:13,670 So let's just also say if I have a driver's license or not. 311 311 00:16:13,710 --> 00:16:16,890 So Jonas is a 40 year old teacher 312 312 00:16:16,890 --> 00:16:21,680 and he has a driver's license. 313 313 00:16:23,040 --> 00:16:26,480 And it says that I have a driver's license 314 314 00:16:26,480 --> 00:16:30,300 because it hasDriversLicense is true 315 315 00:16:30,300 --> 00:16:33,640 but if it was false, then here, it should say 316 316 00:16:33,640 --> 00:16:37,010 and he has no driver's license. 317 317 00:16:37,010 --> 00:16:40,290 So it's either a or no. 318 318 00:16:40,290 --> 00:16:42,820 So figure out how you can do that, 319 319 00:16:42,820 --> 00:16:45,310 and so I hope you manage to do it. 320 320 00:16:45,310 --> 00:16:48,370 It's a bit similar to what we did in the previous lecture 321 321 00:16:48,370 --> 00:16:51,540 but this time I want you to actually write a method 322 322 00:16:51,540 --> 00:16:52,620 on your own. 323 323 00:16:52,620 --> 00:16:55,733 So give this a try and I see you here in a second. 324 324 00:16:58,770 --> 00:17:01,797 Okay. So let's add getSummary 325 325 00:17:05,050 --> 00:17:07,850 and remember that you to a need to have a comma 326 326 00:17:07,850 --> 00:17:09,520 between the properties. 327 327 00:17:09,520 --> 00:17:11,940 And so that's true also with methods, 328 328 00:17:11,940 --> 00:17:13,283 so here we need a comma, 329 329 00:17:14,970 --> 00:17:17,580 and then just a function 330 330 00:17:19,490 --> 00:17:21,930 and it will then get all this data of course, 331 331 00:17:21,930 --> 00:17:24,300 from the current object. 332 332 00:17:24,300 --> 00:17:27,653 So actually let's first call this method, 333 333 00:17:28,900 --> 00:17:31,930 so, and we're doing it inside of console log, 334 334 00:17:31,930 --> 00:17:33,330 log because of course, 335 335 00:17:33,330 --> 00:17:36,660 we want to be able to see the summary string 336 336 00:17:36,660 --> 00:17:38,690 as a message in the console. 337 337 00:17:38,690 --> 00:17:40,560 So jonas.getSummary. 338 338 00:17:44,220 --> 00:17:48,820 Okay. So, which is the object calling the method? 339 339 00:17:48,820 --> 00:17:50,130 It is Jonas. 340 340 00:17:50,130 --> 00:17:54,180 And so therefore, the this keyword inside of getSummary 341 341 00:17:54,180 --> 00:17:55,930 will be Jonas. 342 342 00:17:55,930 --> 00:17:59,433 So I hope that this one is clear at this point. 343 343 00:18:00,270 --> 00:18:03,630 So let's now build a string here, 344 344 00:18:03,630 --> 00:18:05,270 and starting with the name, 345 345 00:18:05,270 --> 00:18:07,950 it is at this.firstName is a, 346 346 00:18:14,250 --> 00:18:15,233 and now the age, 347 347 00:18:16,800 --> 00:18:20,363 so this, and now what do we do here? 348 348 00:18:21,343 --> 00:18:26,300 Should we use the age property, or should we do calcAge? 349 349 00:18:26,300 --> 00:18:29,200 Well, I would say that we should do calcAge 350 350 00:18:29,200 --> 00:18:31,930 because we cannot assume that calcAge 351 351 00:18:31,930 --> 00:18:33,823 was already called before. 352 352 00:18:35,010 --> 00:18:35,843 Okay. 353 353 00:18:35,843 --> 00:18:38,140 And if we don't call calcAge before we call getSummary 354 354 00:18:39,830 --> 00:18:43,230 then the age property would not exist. 355 355 00:18:43,230 --> 00:18:44,063 And so, 356 356 00:18:45,690 --> 00:18:50,323 and so it's, it's better to actually do calcAge here. 357 357 00:18:52,270 --> 00:18:55,070 And so I think we did this before, 358 358 00:18:55,070 --> 00:18:59,240 so in a template string, we can easily do a function call. 359 359 00:18:59,240 --> 00:19:01,300 That's not a problem at all. 360 360 00:19:01,300 --> 00:19:05,700 So this.calcAge will call this other method 361 361 00:19:05,700 --> 00:19:07,423 and this will then return the age. 362 362 00:19:11,520 --> 00:19:14,650 Alright. And maybe it might be strange for you 363 363 00:19:14,650 --> 00:19:17,510 to call the function also on this, 364 364 00:19:17,510 --> 00:19:20,760 but well, the rule is just exactly the same. 365 365 00:19:20,760 --> 00:19:23,700 This is Jonas in this object, 366 366 00:19:23,700 --> 00:19:27,683 and so this is essentially the same as writing it here. 367 367 00:19:29,220 --> 00:19:31,800 Alright. So this will become the age 368 368 00:19:32,980 --> 00:19:37,550 and so, year old, 369 369 00:19:37,550 --> 00:19:41,160 and now the job, jonas.job, 370 370 00:19:41,160 --> 00:19:43,820 and he has, 371 371 00:19:43,820 --> 00:19:47,460 and now we need to decide between a and no. 372 372 00:19:47,460 --> 00:19:50,730 So let's do a turnery operator here. 373 373 00:19:50,730 --> 00:19:53,943 So we get this.DriversLicense, 374 374 00:19:56,490 --> 00:19:58,810 and basically if it's true 375 375 00:19:58,810 --> 00:20:03,380 then we want the results of this operator to be a, 376 376 00:20:03,380 --> 00:20:06,143 and if not, we want it to be no. 377 377 00:20:07,940 --> 00:20:10,350 And then driver's license. 378 378 00:20:12,730 --> 00:20:14,950 Okay? Makes sense? 379 379 00:20:14,950 --> 00:20:19,250 So again, here we want either a or no, 380 380 00:20:19,250 --> 00:20:24,250 depending on the state of the hasDriversLicense property. 381 381 00:20:24,460 --> 00:20:26,180 So we get that property 382 382 00:20:26,180 --> 00:20:27,830 by calling this.hasDriversLicense 383 383 00:20:29,468 --> 00:20:32,130 and here we're using the turnery operator. 384 384 00:20:32,130 --> 00:20:34,863 And so if this first part is true 385 385 00:20:34,863 --> 00:20:37,877 then the result of the operator will be a, 386 386 00:20:37,877 --> 00:20:40,799 and otherwise the result will be no. 387 387 00:20:40,799 --> 00:20:42,997 And so that's what will then be put 388 388 00:20:42,997 --> 00:20:45,664 into this place of the sentence. 389 389 00:20:46,921 --> 00:20:51,373 Okay. And we already called the method down here 390 390 00:20:51,373 --> 00:20:53,373 and we logged it to the console, 391 391 00:20:53,373 --> 00:20:56,725 and so I think this should work now. 392 392 00:20:56,725 --> 00:20:58,217 And it does. 393 393 00:20:58,217 --> 00:21:01,147 So Jonas is a 46 year old teacher 394 394 00:21:01,147 --> 00:21:03,688 and he has a driver's license. 395 395 00:21:03,688 --> 00:21:07,605 Now just to test, let's set it to false and no, 396 396 00:21:09,569 --> 00:21:12,470 and he has no driver's license. 397 397 00:21:12,470 --> 00:21:13,303 Beautiful. 398 398 00:21:16,590 --> 00:21:17,423 Okay. 399 399 00:21:19,000 --> 00:21:21,550 And yeah, that's all the code 400 400 00:21:21,550 --> 00:21:24,670 that I had to show you in this video. 401 401 00:21:24,670 --> 00:21:26,370 And now just to finish the lecture, 402 402 00:21:26,370 --> 00:21:29,610 which I know is already running quite long, 403 403 00:21:29,610 --> 00:21:31,820 but I want to basically build a bridge 404 404 00:21:31,820 --> 00:21:36,060 between this method and the array method lecture. 405 405 00:21:36,060 --> 00:21:39,883 So remember that we used methods on a race previously, 406 406 00:21:40,870 --> 00:21:42,683 so we can quickly go there. 407 407 00:21:43,720 --> 00:21:47,750 So it was before this challenge. 408 408 00:21:47,750 --> 00:21:49,080 Yes, indeed. 409 409 00:21:49,080 --> 00:21:52,550 So for example here we have friends.push. 410 410 00:21:52,550 --> 00:21:56,940 And so we have an array and on there we call a method. 411 411 00:21:56,940 --> 00:21:59,750 So just like we did in this video, 412 412 00:21:59,750 --> 00:22:01,450 now what this means is 413 413 00:22:01,450 --> 00:22:04,770 that arrays are actually also objects, 414 414 00:22:04,770 --> 00:22:07,460 they are just a special kind of object. 415 415 00:22:07,460 --> 00:22:09,880 And so they have functions, or in other words 416 416 00:22:09,880 --> 00:22:13,380 they have methods that we can use to manipulate them 417 417 00:22:13,380 --> 00:22:18,380 like push, pop, shift and unshift and many more. 418 418 00:22:19,390 --> 00:22:21,120 All right? So in this lecture, 419 419 00:22:21,120 --> 00:22:24,610 we created our own methods on our own objects. 420 420 00:22:24,610 --> 00:22:28,780 But here we basically used built in methods on a race. 421 421 00:22:28,780 --> 00:22:30,900 And so once again that means 422 422 00:22:30,900 --> 00:22:34,540 that the race are actually also objects, 423 423 00:22:34,540 --> 00:22:38,360 that's why they can have methods as well. 424 424 00:22:38,360 --> 00:22:42,230 And we will dive deeper into why things work like this, 425 425 00:22:42,230 --> 00:22:46,290 but I wanted you to realize this early on in the course, 426 426 00:22:46,290 --> 00:22:48,610 this is quite a complex topic, 427 427 00:22:48,610 --> 00:22:52,120 and so there is really a very exciting journey 428 428 00:22:52,120 --> 00:22:53,940 still ahead of you. 429 429 00:22:53,940 --> 00:22:56,890 So I hope you're enjoying this journey so far. 430 430 00:22:56,890 --> 00:22:58,250 And now to test your knowledge, 431 431 00:22:58,250 --> 00:23:02,503 there is coding challenge number three, coming up next. 37029