WEBVTT 1 00:01.290 --> 00:03.750 Let's keep exploring objects 2 00:03.750 --> 00:07.473 and this lecture will bring us to object methods. 3 00:08.950 --> 00:11.900 So we learned that objects just like arrays 4 00:11.900 --> 00:14.230 can hold different types of data. 5 00:14.230 --> 00:16.220 And they can hold even arrays, 6 00:16.220 --> 00:20.400 and in fact, they could even hold objects inside objects. 7 00:20.400 --> 00:23.340 But now we can take it even further. 8 00:23.340 --> 00:25.600 And for that, remember how I said 9 00:25.600 --> 00:29.630 that functions are really just another type of value. 10 00:29.630 --> 00:31.950 And if a function is just a value 11 00:31.950 --> 00:35.370 then that means that we can create a key value pair 12 00:35.370 --> 00:37.820 in which the value is a function. 13 00:37.820 --> 00:40.660 And that then means that we can in fact, 14 00:40.660 --> 00:43.280 add functions to objects. 15 00:43.280 --> 00:45.750 And so let's now see how. 16 00:45.750 --> 00:49.030 And once more, I will get back this object here 17 00:50.010 --> 00:55.010 but we will change it up a little bit this time around. 18 00:55.020 --> 00:59.387 So here let's simplify and just put the birthYear. 19 01:00.540 --> 01:02.293 So just 1991. 20 01:03.150 --> 01:07.007 And I also want to add a Boolean here, hasDriversLicense. 21 01:10.760 --> 01:14.010 Just to show you that we can hold all kinds 22 01:14.010 --> 01:17.650 of different data types in one object. 23 01:17.650 --> 01:22.650 But now let's also add a function here as a key value pair. 24 01:22.780 --> 01:27.420 So to do that, all we have to do is to add another key here. 25 01:27.420 --> 01:29.970 And the function that we want to add is again, 26 01:29.970 --> 01:32.500 the calcAge function. 27 01:32.500 --> 01:35.600 So that's one of the favorites, as you can see, 28 01:35.600 --> 01:38.560 but it is because it's a very simple calculation 29 01:38.560 --> 01:41.010 that we can do with the birth year. 30 01:41.010 --> 01:43.870 So to do that, let's simply add the name 31 01:43.870 --> 01:47.060 basically off the function here as a key. 32 01:47.060 --> 01:48.770 So as a property, 33 01:48.770 --> 01:53.330 so calcAge and then the colon, and now here 34 01:53.330 --> 01:56.970 we simply specify the function as an expression 35 01:56.970 --> 02:00.327 and that works because the expression produces the value. 36 02:00.327 --> 02:02.423 And so we can just do this, 37 02:03.850 --> 02:06.810 so function, and just like before , 38 02:06.810 --> 02:08.430 we pass in the birth year 39 02:10.800 --> 02:15.800 and we return 2037 minus the birth year that was passed in. 40 02:19.410 --> 02:24.410 So this is pretty similar to simply writing this, right? 41 02:24.690 --> 02:27.110 So a regular function expression. 42 02:27.110 --> 02:30.283 So const calcAge like this, 43 02:30.283 --> 02:32.680 this is how we used to do it before. 44 02:32.680 --> 02:34.920 And so you see that this is pretty similar. 45 02:34.920 --> 02:36.880 The difference is just in the syntax 46 02:36.880 --> 02:41.070 because now calcAge is not a regular variable like here, 47 02:41.070 --> 02:43.970 but it's a property of the Jonas object. 48 02:43.970 --> 02:46.020 And so therefore we use the colon here 49 02:46.020 --> 02:48.720 but the rest here is exactly the same. 50 02:48.720 --> 02:50.800 And so that's why it was very important 51 02:50.800 --> 02:54.870 that you understood what a function expression actually is 52 02:54.870 --> 02:57.150 because here we need to function expression 53 02:57.150 --> 02:59.230 to create this method. 54 02:59.230 --> 03:02.210 And that's what this function is called. 55 03:02.210 --> 03:04.040 So any function that is attached 56 03:04.040 --> 03:06.643 to an object is called a method. 57 03:07.940 --> 03:10.750 So of course we could have not used 58 03:10.750 --> 03:12.790 a function declaration here. 59 03:12.790 --> 03:14.223 So something like this, 60 03:15.060 --> 03:20.060 so function calcAge, for example, that would not work, 61 03:20.830 --> 03:23.610 we would certainly get an error here. 62 03:23.610 --> 03:26.090 So unexpected token function, 63 03:26.090 --> 03:27.940 because this is a declaration. 64 03:27.940 --> 03:29.620 And so it doesn't work here, 65 03:29.620 --> 03:31.880 here, we need an expression. 66 03:31.880 --> 03:34.530 And so this will work indeed. 67 03:34.530 --> 03:36.870 Okay? Does this make sense? 68 03:36.870 --> 03:41.200 So if you can think of functions as simply being values 69 03:41.200 --> 03:46.010 then you can see that a method is actually also a property. 70 03:46.010 --> 03:47.920 It just happens to be a property 71 03:47.920 --> 03:50.280 that holds a function value. 72 03:50.280 --> 03:52.820 So here we have a string value, 73 03:52.820 --> 03:55.210 here we have an array value, 74 03:55.210 --> 03:56.937 here we have a Boolean value, 75 03:56.937 --> 03:58.693 and here we have a function value. 76 04:00.200 --> 04:01.640 All right. 77 04:01.640 --> 04:04.740 So, I hope that's logical. 78 04:04.740 --> 04:08.120 And now just like we can access any other property, 79 04:08.120 --> 04:12.143 we can also access the calcAge property or method. 80 04:13.410 --> 04:18.410 So jonas.calcAge and so calcAge is now the function value, 81 04:19.520 --> 04:22.680 and just like any other function in order to call it, 82 04:22.680 --> 04:24.800 we use the parenthesis. 83 04:24.800 --> 04:27.860 And now we can pass in the year here. 84 04:27.860 --> 04:29.960 And so that should then calculate our age. 85 04:31.550 --> 04:36.223 And let's just unlock this result to the console here, 86 04:38.980 --> 04:40.763 just to see if everything works. 87 04:41.950 --> 04:44.280 And it does indeed. 88 04:44.280 --> 04:48.640 Okay. And you could also have access 89 04:48.640 --> 04:51.683 to this method using the bracket notation, 90 04:52.730 --> 04:57.080 because again, it's just as if it was a normal property 91 04:57.950 --> 05:01.180 and the brackets would actually be necessary here 92 05:01.180 --> 05:03.930 so that this then here is the function 93 05:03.930 --> 05:06.923 and then we call the function using the parenthesis. 94 05:08.080 --> 05:09.293 So let's try that. 95 05:10.720 --> 05:13.683 And, yeah, here this needs to be a string. 96 05:16.350 --> 05:19.140 So like I showed you in the last lecture, 97 05:19.140 --> 05:22.560 and now here we get 46 as well. 98 05:22.560 --> 05:26.060 Okay. So just like I showed you in the last video 99 05:26.060 --> 05:28.380 with the operator proceedings table, 100 05:28.380 --> 05:30.360 the first thing that happens here, 101 05:30.360 --> 05:33.720 is that jonas.calcAge is computed. 102 05:33.720 --> 05:36.320 And so this here will become the function value. 103 05:36.320 --> 05:38.210 And then with the parenthesis, 104 05:38.210 --> 05:42.567 we call that function value here and passed in 1991. 105 05:42.567 --> 05:44.290 And the same thing here, 106 05:44.290 --> 05:48.110 so here we access the property calcAge using the brackets 107 05:48.110 --> 05:51.040 and then this here will basically be replaced 108 05:51.040 --> 05:52.187 with the function, 109 05:52.187 --> 05:57.123 and then we call the function right here, just like before. 110 05:58.840 --> 06:01.720 All right, now you might have noticed 111 06:01.720 --> 06:05.090 that the birth year 1991, 112 06:05.090 --> 06:07.840 that we passed here as an argument to the method 113 06:07.840 --> 06:09.880 is actually already defined 114 06:09.880 --> 06:14.400 in the Jonas object itself up here, right? 115 06:14.400 --> 06:18.180 So we already have this information in the Jonas object. 116 06:18.180 --> 06:22.840 And so writing the same number here and here is not ideal 117 06:22.840 --> 06:26.510 because we might make a mistake and pass in the wrong year. 118 06:26.510 --> 06:28.510 For example, right here. 119 06:28.510 --> 06:31.290 So Jonas' birth year is 91 120 06:31.290 --> 06:35.570 but here, we could, for some reason accidentally do 92 121 06:35.570 --> 06:37.180 and then it would be wrong. 122 06:37.180 --> 06:40.280 And even if we do not make any mistake, 123 06:40.280 --> 06:42.130 this is still not ideal 124 06:42.130 --> 06:45.090 because we are not keeping the code dry. 125 06:45.090 --> 06:49.170 So we're violating the don't repeat yourself principle. 126 06:49.170 --> 06:51.680 So if we know the birth year of Jonas, 127 06:51.680 --> 06:54.320 it would only be written in one place, 128 06:54.320 --> 06:55.970 not in multiple places, 129 06:55.970 --> 06:57.490 because if that might change, 130 06:57.490 --> 06:59.440 then we have to change it everywhere. 131 06:59.440 --> 07:03.290 That's always the philosophy that we need to keep in mind. 132 07:03.290 --> 07:07.650 So what if we could actually access this birth year property 133 07:07.650 --> 07:10.190 directly from the Jonas object 134 07:10.190 --> 07:12.890 instead of having to pass it in? 135 07:12.890 --> 07:16.370 Well, it turns out that we actually can, 136 07:16.370 --> 07:18.500 and that's because in every method, 137 07:18.500 --> 07:20.810 JavaScript gives us access 138 07:20.810 --> 07:24.110 to a special variable called this. 139 07:24.110 --> 07:28.230 And so what we can do now is in this calcAge function, 140 07:28.230 --> 07:30.210 we can read the birth year directly 141 07:30.210 --> 07:33.940 from this object itself without having to pass it in 142 07:33.940 --> 07:36.993 as a parameter here into this function. 143 07:38.130 --> 07:42.680 Alright, so let me copy this and comment this one out 144 07:42.680 --> 07:46.560 just so that we keep a record of what we did 145 07:46.560 --> 07:48.683 but this here will be the new version. 146 07:50.360 --> 07:53.900 So now we no longer need this parameter 147 07:53.900 --> 07:58.370 and we will read the birth year directly from the object. 148 07:58.370 --> 08:02.290 And for that again, we will use the this keyword. 149 08:02.290 --> 08:03.930 So the this key word 150 08:03.930 --> 08:08.190 or the this variable is basically equal to the object 151 08:08.190 --> 08:10.930 on which the method is called, 152 08:10.930 --> 08:12.260 or in other words, 153 08:12.260 --> 08:15.750 it is equal to the object calling the method. 154 08:15.750 --> 08:18.103 So, let's see who is calling the method. 155 08:19.260 --> 08:22.518 So down here, here is calcAge, 156 08:22.518 --> 08:26.620 and the object that is calling the method is Jonas, 157 08:26.620 --> 08:28.960 because that's where the dot is. 158 08:28.960 --> 08:30.650 And let's forget about this one, 159 08:30.650 --> 08:32.860 actually comment it out here. 160 08:32.860 --> 08:34.310 And so again 161 08:34.310 --> 08:38.970 the object that is calling the calcAge method here is Jonas. 162 08:38.970 --> 08:42.130 And so that means that inside this method 163 08:42.130 --> 08:47.130 the this variable or the this keyword will point to Jonas. 164 08:47.360 --> 08:51.370 And so let me just write this.birthYear here 165 08:51.370 --> 08:54.723 and then I can explain it even a little bit better. 166 08:55.580 --> 09:00.010 So, here we don't need to pass the 1991 here 167 09:00.940 --> 09:05.260 and I will run this now and we still get the correct result. 168 09:05.260 --> 09:07.140 So, great. 169 09:07.140 --> 09:09.593 And to make this even more clear here, 170 09:11.090 --> 09:14.563 let's also log this to the console, 171 09:17.660 --> 09:21.860 and indeed, this is the whole Jonas object. 172 09:21.860 --> 09:25.030 And so again, that's because the Jonas object 173 09:25.030 --> 09:27.950 is the one who is calling this method, 174 09:27.950 --> 09:29.920 so this function, 175 09:29.920 --> 09:33.290 see here, it's jonas.calcAge 176 09:33.290 --> 09:35.940 and so whatever appears before the dot 177 09:35.940 --> 09:37.920 is the one who is calling the method. 178 09:37.920 --> 09:40.200 And so therefore, in the method, 179 09:40.200 --> 09:43.280 this points to Jonas now, 180 09:43.280 --> 09:45.430 and if this points to Jonas, 181 09:45.430 --> 09:48.420 then this.birthYear is of course 182 09:48.420 --> 09:51.520 this value that we have right here. 183 09:51.520 --> 09:52.370 Great. 184 09:52.370 --> 09:54.260 So you see that the this keyword 185 09:54.260 --> 09:56.870 is something really, really useful 186 09:56.870 --> 09:59.670 and we will learn even more about the this keyword 187 09:59.670 --> 10:02.680 in greater detail in a later section. 188 10:02.680 --> 10:06.380 For now, I just wanted to introduce you to this concept 189 10:06.380 --> 10:09.760 and I noticed can be a bit confusing. 190 10:09.760 --> 10:12.540 So really make sure to maybe pause the video 191 10:12.540 --> 10:16.120 and really analyze what's happening here. 192 10:16.120 --> 10:18.090 Maybe you can even rewind a little bit 193 10:18.090 --> 10:20.100 and hear my explanation again, 194 10:20.100 --> 10:22.210 that might be useful too. 195 10:22.210 --> 10:25.380 Now you might argue that maybe we don't even need 196 10:25.380 --> 10:27.360 this confusing this keywords. 197 10:27.360 --> 10:31.363 Why not just do jonas.birthYear, here instead? 198 10:32.300 --> 10:35.520 Well, because that would actually still violate 199 10:35.520 --> 10:38.320 the don't repeat yourself principle. 200 10:38.320 --> 10:40.830 It would work just the same here now, 201 10:40.830 --> 10:41.930 but then let's say 202 10:41.930 --> 10:44.690 that we need to change the name of the object. 203 10:44.690 --> 10:47.150 So we change it here to Jonas2 204 10:47.150 --> 10:49.580 and then we call Jonas2 down here, 205 10:49.580 --> 10:52.683 and then the code will no longer automatically work, 206 10:53.630 --> 10:57.010 because now Jonas is not defined of course. 207 10:57.010 --> 10:59.540 And so we would have to keep that in mind 208 10:59.540 --> 11:02.870 and then come here and manually change this as well, 209 11:02.870 --> 11:05.780 while if we had the this keyword, 210 11:05.780 --> 11:07.910 then everything will keep working 211 11:07.910 --> 11:09.980 without us having to change it there, 212 11:09.980 --> 11:13.490 because now this will simply point to Jonas2, 213 11:13.490 --> 11:16.320 because that is the object calling the method. 214 11:16.320 --> 11:19.540 And so therefore it's always a good idea 215 11:19.540 --> 11:22.090 to reference the object itself 216 11:22.090 --> 11:24.553 and not hard-code the name of the object. 217 11:25.920 --> 11:30.920 So let's put it back to Jonas and yeah, much better. 218 11:33.130 --> 11:35.170 So this works great already, 219 11:35.170 --> 11:36.340 and we're really going 220 11:36.340 --> 11:39.450 into some more advanced territory here. 221 11:39.450 --> 11:41.330 So I hope you're still following me 222 11:41.330 --> 11:44.610 and you're still making sense of everything. 223 11:44.610 --> 11:48.320 However, we can actually even take this a little bit further 224 11:49.230 --> 11:53.000 but don't worry, it's not going to get a lot more confusing, 225 11:53.000 --> 11:55.560 just a small variation of this, 226 11:55.560 --> 11:57.850 because let's say that we need to access 227 11:57.850 --> 12:01.383 the age multiple times throughout our program. 228 12:02.390 --> 12:06.723 So that would be like calling this a couple of times. 229 12:07.940 --> 12:10.700 So let's say in three places of our application, 230 12:10.700 --> 12:12.690 we need to access the age, 231 12:12.690 --> 12:15.103 and so, of course this will work, 232 12:16.510 --> 12:18.260 and indeed it does. 233 12:18.260 --> 12:21.350 And it always locks the Jonas object 234 12:21.350 --> 12:22.950 because we still have this here. 235 12:24.280 --> 12:26.963 So this makes it a bit easier to view. 236 12:27.860 --> 12:29.380 And so what happens here 237 12:29.380 --> 12:33.360 is that a function will get called a total of four times. 238 12:33.360 --> 12:37.730 And so this computation here will be done four times. 239 12:37.730 --> 12:39.870 And in this case that's not a big deal 240 12:39.870 --> 12:42.830 but it might be a like a heavier computation 241 12:42.830 --> 12:45.160 that actually takes some more time, 242 12:45.160 --> 12:49.560 and so it would be a bad practice to do this multiple times. 243 12:49.560 --> 12:53.300 Instead, what we can do is to just calculate the age once, 244 12:53.300 --> 12:55.610 then store it in the object, 245 12:55.610 --> 12:58.050 and then when we need it at a later point, 246 12:58.050 --> 13:00.090 we can then just retrieve the age 247 13:00.090 --> 13:02.900 as a property from the object. 248 13:02.900 --> 13:05.213 So, I hope you're following me here. 249 13:07.170 --> 13:10.090 So I will again copy this and comment it out 250 13:10.090 --> 13:14.790 so that we keep all the three versions that we did here. 251 13:14.790 --> 13:16.770 So, what I was trying to say 252 13:16.770 --> 13:19.780 is that we can now use the this keyword 253 13:19.780 --> 13:22.023 also to store a new property. 254 13:22.860 --> 13:27.860 So, we can say this.age is equal to this here. 255 13:31.694 --> 13:33.490 So we calculate the age, 256 13:33.490 --> 13:37.280 and then we create a new property on the current object. 257 13:37.280 --> 13:40.450 So in this case, on the Jonas object, 258 13:40.450 --> 13:43.830 and remember that we can use the dot notation like this 259 13:43.830 --> 13:46.320 to create new properties. 260 13:46.320 --> 13:48.723 So we did that in a previous lecture as well. 261 13:51.130 --> 13:53.030 Where was that? 262 13:53.030 --> 13:54.180 Yeah, right here. 263 13:54.180 --> 13:56.600 So here we created jonas.location 264 13:56.600 --> 13:58.290 and set it to Portugal. 265 13:58.290 --> 14:02.430 And so here we are essentially creating jonas.age 266 14:02.430 --> 14:06.360 and setting it to this age that we just calculated. 267 14:06.360 --> 14:09.930 And then we can simply return this age. 268 14:09.930 --> 14:13.150 And of course we don't even need to return anything 269 14:13.150 --> 14:14.580 if we didn't want to. 270 14:14.580 --> 14:17.720 We could make this method only calculate the age 271 14:17.720 --> 14:19.550 but not even return it, 272 14:19.550 --> 14:21.160 but I think it's a good practice 273 14:21.160 --> 14:22.973 to actually also return it. 274 14:23.992 --> 14:26.650 And so now here we can replace the function call 275 14:26.650 --> 14:28.620 with simply a request 276 14:28.620 --> 14:31.000 for the age property, 277 14:31.000 --> 14:33.810 and notice this trick that I did here again 278 14:33.810 --> 14:35.920 with the command D, right, 279 14:35.920 --> 14:38.150 So this gives me multiple cursors 280 14:38.150 --> 14:40.270 and then I can do one operation 281 14:40.270 --> 14:42.830 in multiple places at the same time. 282 14:42.830 --> 14:44.570 So that's a really handy shortcut. 283 14:44.570 --> 14:48.000 So, again, command D, or control D 284 14:48.000 --> 14:52.433 and in the menu bar that means add next occurrence. 285 14:53.780 --> 14:57.053 So let's test this and the results should be the same, 286 14:58.410 --> 15:02.940 and it is, but we only needed to calculate the age once 287 15:02.940 --> 15:04.060 then from here, 288 15:04.060 --> 15:05.833 we simply retrieve the property 289 15:05.833 --> 15:08.470 that we had already calculated before. 290 15:08.470 --> 15:11.973 And so this is the most efficient solution let's say. 291 15:13.130 --> 15:15.880 All right, and now I actually have another, 292 15:15.880 --> 15:17.680 a small challenge for you 293 15:17.680 --> 15:20.260 that you can do just in this video. 294 15:20.260 --> 15:24.302 So I want you to write a method called getSummary 295 15:24.302 --> 15:26.720 and this method should return a string 296 15:26.720 --> 15:30.640 which should kind of summarize the data about Jonas, 297 15:30.640 --> 15:33.130 or, of course, any other person data 298 15:33.130 --> 15:34.583 that you might have used. 299 15:36.340 --> 15:37.423 For example, 300 15:38.760 --> 15:39.593 let me again, 301 15:41.090 --> 15:43.550 actually we can get rid of this. 302 15:43.550 --> 15:46.370 So let me write Challenge here again 303 15:46.370 --> 15:48.193 and then do an example string. 304 15:49.850 --> 15:52.400 So I want you to write for example this, 305 15:52.400 --> 15:57.400 Jonas is a 46 year old teacher. 306 16:01.010 --> 16:03.710 And we now could actually add all the data here 307 16:03.710 --> 16:04.800 to the string, 308 16:04.800 --> 16:07.150 but that would be too much work 309 16:07.150 --> 16:08.670 and I'm a bit lazy now. 310 16:08.670 --> 16:13.670 So let's just also say if I have a driver's license or not. 311 16:13.710 --> 16:16.890 So Jonas is a 40 year old teacher 312 16:16.890 --> 16:21.680 and he has a driver's license. 313 16:23.040 --> 16:26.480 And it says that I have a driver's license 314 16:26.480 --> 16:30.300 because it hasDriversLicense is true 315 16:30.300 --> 16:33.640 but if it was false, then here, it should say 316 16:33.640 --> 16:37.010 and he has no driver's license. 317 16:37.010 --> 16:40.290 So it's either a or no. 318 16:40.290 --> 16:42.820 So figure out how you can do that, 319 16:42.820 --> 16:45.310 and so I hope you manage to do it. 320 16:45.310 --> 16:48.370 It's a bit similar to what we did in the previous lecture 321 16:48.370 --> 16:51.540 but this time I want you to actually write a method 322 16:51.540 --> 16:52.620 on your own. 323 16:52.620 --> 16:55.733 So give this a try and I see you here in a second. 324 16:58.770 --> 17:01.797 Okay. So let's add getSummary 325 17:05.050 --> 17:07.850 and remember that you to a need to have a comma 326 17:07.850 --> 17:09.520 between the properties. 327 17:09.520 --> 17:11.940 And so that's true also with methods, 328 17:11.940 --> 17:13.283 so here we need a comma, 329 17:14.970 --> 17:17.580 and then just a function 330 17:19.490 --> 17:21.930 and it will then get all this data of course, 331 17:21.930 --> 17:24.300 from the current object. 332 17:24.300 --> 17:27.653 So actually let's first call this method, 333 17:28.900 --> 17:31.930 so, and we're doing it inside of console log, 334 17:31.930 --> 17:33.330 log because of course, 335 17:33.330 --> 17:36.660 we want to be able to see the summary string 336 17:36.660 --> 17:38.690 as a message in the console. 337 17:38.690 --> 17:40.560 So jonas.getSummary. 338 17:44.220 --> 17:48.820 Okay. So, which is the object calling the method? 339 17:48.820 --> 17:50.130 It is Jonas. 340 17:50.130 --> 17:54.180 And so therefore, the this keyword inside of getSummary 341 17:54.180 --> 17:55.930 will be Jonas. 342 17:55.930 --> 17:59.433 So I hope that this one is clear at this point. 343 18:00.270 --> 18:03.630 So let's now build a string here, 344 18:03.630 --> 18:05.270 and starting with the name, 345 18:05.270 --> 18:07.950 it is at this.firstName is a, 346 18:14.250 --> 18:15.233 and now the age, 347 18:16.800 --> 18:20.363 so this, and now what do we do here? 348 18:21.343 --> 18:26.300 Should we use the age property, or should we do calcAge? 349 18:26.300 --> 18:29.200 Well, I would say that we should do calcAge 350 18:29.200 --> 18:31.930 because we cannot assume that calcAge 351 18:31.930 --> 18:33.823 was already called before. 352 18:35.010 --> 18:35.843 Okay. 353 18:35.843 --> 18:38.140 And if we don't call calcAge before we call getSummary 354 18:39.830 --> 18:43.230 then the age property would not exist. 355 18:43.230 --> 18:44.063 And so, 356 18:45.690 --> 18:50.323 and so it's, it's better to actually do calcAge here. 357 18:52.270 --> 18:55.070 And so I think we did this before, 358 18:55.070 --> 18:59.240 so in a template string, we can easily do a function call. 359 18:59.240 --> 19:01.300 That's not a problem at all. 360 19:01.300 --> 19:05.700 So this.calcAge will call this other method 361 19:05.700 --> 19:07.423 and this will then return the age. 362 19:11.520 --> 19:14.650 Alright. And maybe it might be strange for you 363 19:14.650 --> 19:17.510 to call the function also on this, 364 19:17.510 --> 19:20.760 but well, the rule is just exactly the same. 365 19:20.760 --> 19:23.700 This is Jonas in this object, 366 19:23.700 --> 19:27.683 and so this is essentially the same as writing it here. 367 19:29.220 --> 19:31.800 Alright. So this will become the age 368 19:32.980 --> 19:37.550 and so, year old, 369 19:37.550 --> 19:41.160 and now the job, jonas.job, 370 19:41.160 --> 19:43.820 and he has, 371 19:43.820 --> 19:47.460 and now we need to decide between a and no. 372 19:47.460 --> 19:50.730 So let's do a turnery operator here. 373 19:50.730 --> 19:53.943 So we get this.DriversLicense, 374 19:56.490 --> 19:58.810 and basically if it's true 375 19:58.810 --> 20:03.380 then we want the results of this operator to be a, 376 20:03.380 --> 20:06.143 and if not, we want it to be no. 377 20:07.940 --> 20:10.350 And then driver's license. 378 20:12.730 --> 20:14.950 Okay? Makes sense? 379 20:14.950 --> 20:19.250 So again, here we want either a or no, 380 20:19.250 --> 20:24.250 depending on the state of the hasDriversLicense property. 381 20:24.460 --> 20:26.180 So we get that property 382 20:26.180 --> 20:27.830 by calling this.hasDriversLicense 383 20:29.468 --> 20:32.130 and here we're using the turnery operator. 384 20:32.130 --> 20:34.863 And so if this first part is true 385 20:34.863 --> 20:37.877 then the result of the operator will be a, 386 20:37.877 --> 20:40.799 and otherwise the result will be no. 387 20:40.799 --> 20:42.997 And so that's what will then be put 388 20:42.997 --> 20:45.664 into this place of the sentence. 389 20:46.921 --> 20:51.373 Okay. And we already called the method down here 390 20:51.373 --> 20:53.373 and we logged it to the console, 391 20:53.373 --> 20:56.725 and so I think this should work now. 392 20:56.725 --> 20:58.217 And it does. 393 20:58.217 --> 21:01.147 So Jonas is a 46 year old teacher 394 21:01.147 --> 21:03.688 and he has a driver's license. 395 21:03.688 --> 21:07.605 Now just to test, let's set it to false and no, 396 21:09.569 --> 21:12.470 and he has no driver's license. 397 21:12.470 --> 21:13.303 Beautiful. 398 21:16.590 --> 21:17.423 Okay. 399 21:19.000 --> 21:21.550 And yeah, that's all the code 400 21:21.550 --> 21:24.670 that I had to show you in this video. 401 21:24.670 --> 21:26.370 And now just to finish the lecture, 402 21:26.370 --> 21:29.610 which I know is already running quite long, 403 21:29.610 --> 21:31.820 but I want to basically build a bridge 404 21:31.820 --> 21:36.060 between this method and the array method lecture. 405 21:36.060 --> 21:39.883 So remember that we used methods on arrays previously, 406 21:40.870 --> 21:42.683 so we can quickly go there. 407 21:43.720 --> 21:47.750 So it was before this challenge. 408 21:47.750 --> 21:49.080 Yes, indeed. 409 21:49.080 --> 21:52.550 So for example here we have friends.push. 410 21:52.550 --> 21:56.940 And so we have an array and on there we call a method. 411 21:56.940 --> 21:59.750 So just like we did in this video, 412 21:59.750 --> 22:01.450 now what this means is 413 22:01.450 --> 22:04.770 that arrays are actually also objects, 414 22:04.770 --> 22:07.460 they are just a special kind of object. 415 22:07.460 --> 22:09.880 And so they have functions, or in other words 416 22:09.880 --> 22:13.380 they have methods that we can use to manipulate them 417 22:13.380 --> 22:18.380 like push, pop, shift and unshift and many more. 418 22:19.390 --> 22:21.120 All right? So in this lecture, 419 22:21.120 --> 22:24.610 we created our own methods on our own objects. 420 22:24.610 --> 22:28.780 But here we basically used built-in methods on arrays. 421 22:28.780 --> 22:30.900 And so once again that means 422 22:30.900 --> 22:34.540 that arrays are actually also objects, 423 22:34.540 --> 22:38.360 that's why they can have methods as well. 424 22:38.360 --> 22:42.230 And we will dive deeper into why things work like this, 425 22:42.230 --> 22:46.290 but I wanted you to realize this early on in the course, 426 22:46.290 --> 22:48.610 this is quite a complex topic, 427 22:48.610 --> 22:52.120 and so there is really a very exciting journey 428 22:52.120 --> 22:53.940 still ahead of you. 429 22:53.940 --> 22:56.890 So I hope you're enjoying this journey so far. 430 22:56.890 --> 22:58.250 And now to test your knowledge, 431 22:58.250 --> 23:02.503 there is coding challenge number three, coming up next.