WEBVTT 1 00:00:01.080 --> 00:00:03.450 So we've covered a lot of ground 2 00:00:03.450 --> 00:00:06.180 and learned so many more array methods 3 00:00:06.180 --> 00:00:08.460 over these last few lectures. 4 00:00:08.460 --> 00:00:12.060 And so now it's time for yet another coding challenge 5 00:00:12.060 --> 00:00:15.120 so that you don't forget all of these methods 6 00:00:15.120 --> 00:00:18.423 before we move on to learning even more of them. 7 00:00:19.691 --> 00:00:22.950 And this time around Julia and Kate are studying 8 00:00:22.950 --> 00:00:26.400 the activity levels of different dog breeds. 9 00:00:26.400 --> 00:00:31.400 And so here are your seven tasks, plus one bonus task. 10 00:00:31.440 --> 00:00:33.480 Now these are a lot, 11 00:00:33.480 --> 00:00:35.790 and so I'm not gonna read them here one by one. 12 00:00:35.790 --> 00:00:39.000 So you can just, after you pause the video, 13 00:00:39.000 --> 00:00:43.140 read each of the tasks and then complete them one by one. 14 00:00:43.140 --> 00:00:45.930 Now the test data here is actually a lot. 15 00:00:45.930 --> 00:00:49.170 So it's this huge array of objects. 16 00:00:49.170 --> 00:00:51.360 And so if you don't want to type 17 00:00:51.360 --> 00:00:53.820 all of this here one by one, 18 00:00:53.820 --> 00:00:57.180 please make sure to go to the final files 19 00:00:57.180 --> 00:00:58.980 of this section 20 00:00:58.980 --> 00:01:01.860 and just copy this data structure from there. 21 00:01:01.860 --> 00:01:05.580 And I believe that you already did the same thing earlier 22 00:01:05.580 --> 00:01:07.560 with some other data structure 23 00:01:07.560 --> 00:01:10.800 in some of the other challenges. 24 00:01:10.800 --> 00:01:14.190 All right, so again, here are your tasks. 25 00:01:14.190 --> 00:01:16.500 And so pause the video right now 26 00:01:16.500 --> 00:01:18.840 in order to complete them one by one. 27 00:01:18.840 --> 00:01:21.420 I just need to tell you that some of these 28 00:01:21.420 --> 00:01:23.760 are actually not that easy 29 00:01:23.760 --> 00:01:26.490 and you really need to combine many of the methods 30 00:01:26.490 --> 00:01:28.860 that we have learned up until now. 31 00:01:28.860 --> 00:01:30.090 So for some of these, 32 00:01:30.090 --> 00:01:32.760 you will really have to think quite a bit, 33 00:01:32.760 --> 00:01:36.750 but that's also why these are called challenges, right? 34 00:01:36.750 --> 00:01:39.000 If they were super straightforward, 35 00:01:39.000 --> 00:01:41.880 then you also wouldn't learn a whole lot. 36 00:01:41.880 --> 00:01:43.290 But in any case, 37 00:01:43.290 --> 00:01:46.020 if some of these you were not able to complete, 38 00:01:46.020 --> 00:01:48.240 that's absolutely no problem at all. 39 00:01:48.240 --> 00:01:53.010 As always, just watch the solution a bit later, all right? 40 00:01:53.010 --> 00:01:56.250 But please at least try and pause the video right now 41 00:01:56.250 --> 00:01:59.703 and I see you back here in half an hour or so. 42 00:02:02.730 --> 00:02:05.610 All right, let's get started. 43 00:02:05.610 --> 00:02:08.493 So hopefully the first one was not that hard. 44 00:02:09.330 --> 00:02:11.943 So let's create that variable huskyweight. 45 00:02:15.810 --> 00:02:19.230 And so the task here was to get the average weight 46 00:02:19.230 --> 00:02:24.230 of the huskies and then just store it in its variable. 47 00:02:24.480 --> 00:02:28.260 So basically what I wanted you to do is to find the object 48 00:02:28.260 --> 00:02:32.700 where the breed is husky and then you just store 49 00:02:32.700 --> 00:02:36.450 or you just get the weight from there and store it here. 50 00:02:36.450 --> 00:02:40.830 So we just take the breeds objects. 51 00:02:40.830 --> 00:02:43.173 Well, actually we need to copy this down here, 52 00:02:44.640 --> 00:02:49.233 or I will just close off the comment here. 53 00:02:50.700 --> 00:02:54.153 Remove this, and I guess this one is not so important. 54 00:02:55.110 --> 00:02:59.700 So let's just do breeds.find. 55 00:02:59.700 --> 00:03:03.690 And then each one in there is a breed, let's say. 56 00:03:03.690 --> 00:03:08.070 And then we get breed.breed. 57 00:03:08.070 --> 00:03:10.380 So it could be also called here the name. 58 00:03:10.380 --> 00:03:12.630 So basically the name of the breed, 59 00:03:12.630 --> 00:03:14.730 but it also works like this. 60 00:03:14.730 --> 00:03:19.730 And so then this one should be equal to Husky. 61 00:03:20.220 --> 00:03:22.500 So this one right here. 62 00:03:22.500 --> 00:03:25.230 So this husky weight right now 63 00:03:25.230 --> 00:03:27.630 will be this object right here. 64 00:03:27.630 --> 00:03:32.193 And so from there, we now want to take the average weight. 65 00:03:33.840 --> 00:03:35.613 So lock this to the console. 66 00:03:37.890 --> 00:03:40.440 And so this should give us 26. 67 00:03:40.440 --> 00:03:43.350 And beautiful, there we go. 68 00:03:43.350 --> 00:03:44.643 So this is number one. 69 00:03:48.240 --> 00:03:50.520 Let's move on to number two 70 00:03:50.520 --> 00:03:53.190 and find the name of the only breed 71 00:03:53.190 --> 00:03:57.300 that likes the activities of running and fetch. 72 00:03:57.300 --> 00:04:01.290 And so this one is actually a little bit more complex. 73 00:04:01.290 --> 00:04:05.610 So let's do again, breeds.find, 74 00:04:05.610 --> 00:04:08.190 because the instruction is pretty clear 75 00:04:08.190 --> 00:04:10.590 that this one is again about finding, 76 00:04:10.590 --> 00:04:14.730 and it makes sense that only one breed will be found here 77 00:04:14.730 --> 00:04:17.850 because the find method will indeed only find 78 00:04:17.850 --> 00:04:19.290 the very first occurrence 79 00:04:19.290 --> 00:04:22.770 for which the callback is true in the array. 80 00:04:22.770 --> 00:04:27.330 So just as we learned in the lecture about the find method. 81 00:04:27.330 --> 00:04:32.330 But anyway, here again, we have or callback function now. 82 00:04:33.780 --> 00:04:35.010 And so here, remember, 83 00:04:35.010 --> 00:04:38.580 we now need something that returns a Boolean. 84 00:04:38.580 --> 00:04:41.850 So here we have these activities in these arrays. 85 00:04:41.850 --> 00:04:45.090 And so basically what we want is to find a breed 86 00:04:45.090 --> 00:04:47.430 where the activities array 87 00:04:47.430 --> 00:04:50.970 contains both running and fetch. 88 00:04:50.970 --> 00:04:53.343 So let's do that actually here manually. 89 00:04:54.840 --> 00:04:57.090 So this is gonna be the one. 90 00:04:57.090 --> 00:05:01.563 So this is the Dalmatian or whatever this is called. 91 00:05:03.030 --> 00:05:05.880 And so this activities array here 92 00:05:05.880 --> 00:05:08.640 contains both running and fetch, 93 00:05:08.640 --> 00:05:12.000 which is exactly what the task demands. 94 00:05:12.000 --> 00:05:13.380 And this is the only one. 95 00:05:13.380 --> 00:05:14.880 And so this will be the result. 96 00:05:14.880 --> 00:05:18.570 But now we need to, of course, find this programmatically, 97 00:05:18.570 --> 00:05:21.420 but we actually already set what we need. 98 00:05:21.420 --> 00:05:24.210 So again, this array here needs to contain 99 00:05:24.210 --> 00:05:28.290 both running and fetch. 100 00:05:28.290 --> 00:05:30.590 So let's just write that here in our callback. 101 00:05:31.590 --> 00:05:35.850 So breed.activities needs to, 102 00:05:35.850 --> 00:05:39.963 and it's not called contain, but includes in JavaScript. 103 00:05:41.580 --> 00:05:45.870 And so it needs to contain, so to include fetch. 104 00:05:45.870 --> 00:05:49.780 And now it needs to also include running. 105 00:05:52.560 --> 00:05:54.750 So we just do the same thing again. 106 00:05:54.750 --> 00:05:58.503 So breed.activities.includes, 107 00:06:01.560 --> 00:06:03.363 and then running. 108 00:06:04.260 --> 00:06:07.410 So both of these will return a Boolean. 109 00:06:07.410 --> 00:06:08.910 So true, false. 110 00:06:08.910 --> 00:06:11.793 So this one here will return true for many of them. 111 00:06:12.630 --> 00:06:14.940 So this one here has fetch, so it'll be true, 112 00:06:14.940 --> 00:06:17.220 in this case, it'll be true here 113 00:06:17.220 --> 00:06:20.250 and here and in many others. 114 00:06:20.250 --> 00:06:21.870 But then here we have this and. 115 00:06:21.870 --> 00:06:24.687 And so this one will also return true or false. 116 00:06:24.687 --> 00:06:27.870 And so then only the one for which this is true 117 00:06:27.870 --> 00:06:32.250 and this is true, will become a true this entire expression. 118 00:06:32.250 --> 00:06:35.340 And so then that's the breed, that will be fine. 119 00:06:35.340 --> 00:06:37.920 Let's also store it in the variable 120 00:06:37.920 --> 00:06:39.840 that is set in the instruction, 121 00:06:39.840 --> 00:06:41.973 which is dogBothActivities. 122 00:06:47.940 --> 00:06:50.610 Let's store that in here 123 00:06:50.610 --> 00:06:52.030 and log to the console 124 00:06:55.230 --> 00:06:56.700 exactly this. 125 00:06:56.700 --> 00:07:00.390 And indeed it is this one with this name right here. 126 00:07:00.390 --> 00:07:03.660 And let's actually only get the breed itself. 127 00:07:03.660 --> 00:07:06.810 So .breed, 128 00:07:06.810 --> 00:07:08.253 and beautiful. 129 00:07:10.200 --> 00:07:12.150 So done. 130 00:07:12.150 --> 00:07:15.780 Again, maybe a little bit more difficult, this one here. 131 00:07:15.780 --> 00:07:17.460 But you can do it. 132 00:07:17.460 --> 00:07:20.940 And if not, again, no problem in just watching the solution 133 00:07:20.940 --> 00:07:22.560 as you're doing right now. 134 00:07:22.560 --> 00:07:23.850 Next in number three, 135 00:07:23.850 --> 00:07:26.760 we should create an array called allActivities. 136 00:07:26.760 --> 00:07:29.160 Let's write that here right away. 137 00:07:29.160 --> 00:07:32.400 allActivities, which as the name says, 138 00:07:32.400 --> 00:07:37.350 should contain all the activities of all the dog breeds. 139 00:07:37.350 --> 00:07:39.963 So for this we can just use a map. 140 00:07:41.460 --> 00:07:44.640 So breeds.map 141 00:07:44.640 --> 00:07:46.773 and then breed. 142 00:07:48.510 --> 00:07:52.250 And then here we want to just get the breed.activities. 143 00:07:54.540 --> 00:07:55.373 Right? 144 00:07:56.490 --> 00:07:59.310 Now, we're not done here yet, but it's a start. 145 00:07:59.310 --> 00:08:01.323 So let's see what we have so far. 146 00:08:03.210 --> 00:08:06.660 And so here we have this array of arrays. 147 00:08:06.660 --> 00:08:11.660 So these are exactly all of these activities right here. 148 00:08:13.020 --> 00:08:17.220 However, the instruction says that we should have one array 149 00:08:17.220 --> 00:08:20.550 of all the activities, not an array of arrays. 150 00:08:20.550 --> 00:08:24.300 And so here is where we can use that flat method 151 00:08:24.300 --> 00:08:25.983 that we also just learned about. 152 00:08:27.060 --> 00:08:31.050 And so now we indeed get this one array. 153 00:08:31.050 --> 00:08:35.760 Now, as an alternative, whenever we use map and then flat, 154 00:08:35.760 --> 00:08:39.390 we can just use the flatMap method instead. 155 00:08:39.390 --> 00:08:42.150 So which is basically a two in one. 156 00:08:42.150 --> 00:08:44.133 So let's just replace this. 157 00:08:45.450 --> 00:08:47.760 We'll comment this one out. 158 00:08:47.760 --> 00:08:52.110 And so again, as I just mentioned, let's use flatMap, 159 00:08:52.110 --> 00:08:54.510 then we can remove this one 160 00:08:54.510 --> 00:08:56.733 and we get the exact same result. 161 00:08:57.600 --> 00:08:58.620 Beautiful. 162 00:08:58.620 --> 00:09:00.210 That's done as well. 163 00:09:00.210 --> 00:09:02.910 Onto the next one, which says, create an array, 164 00:09:02.910 --> 00:09:07.910 uniqueActivities that contains only the unique activities. 165 00:09:08.160 --> 00:09:11.730 So basically no repetitions of the activities 166 00:09:11.730 --> 00:09:13.200 as we have right now. 167 00:09:13.200 --> 00:09:16.110 So currently we have running here multiple times, 168 00:09:16.110 --> 00:09:19.170 we have fetch, fetch, here fetch again. 169 00:09:19.170 --> 00:09:22.380 And so of course, this doesn't make so much sense. 170 00:09:22.380 --> 00:09:24.993 So let's create that new variable, 171 00:09:26.284 --> 00:09:28.410 uniqueActivities. 172 00:09:28.410 --> 00:09:30.030 And this one is pretty easy. 173 00:09:30.030 --> 00:09:33.540 So for this, we can just make use of the property 174 00:09:33.540 --> 00:09:36.180 that sets are always unique. 175 00:09:36.180 --> 00:09:39.000 So all the values in a set are unique. 176 00:09:39.000 --> 00:09:43.500 So we can just create a new set 177 00:09:43.500 --> 00:09:47.133 and pass in the all activities that we already have, 178 00:09:49.080 --> 00:09:52.713 again, logging it to the console to see our progress. 179 00:09:54.030 --> 00:09:56.700 And so now we get this set 180 00:09:56.700 --> 00:10:00.990 which contains only the six different activities that exist. 181 00:10:00.990 --> 00:10:04.860 And so now finally, we can convert this to an array. 182 00:10:04.860 --> 00:10:07.510 So let's just select this here 183 00:10:08.640 --> 00:10:10.980 and then just spreading all the elements 184 00:10:10.980 --> 00:10:12.900 of the set into the new array. 185 00:10:12.900 --> 00:10:16.263 And so then here, this is our final result. 186 00:10:17.520 --> 00:10:20.700 So mark, this one as done as well. 187 00:10:20.700 --> 00:10:24.030 And so moving on, we go to number five, 188 00:10:24.030 --> 00:10:27.690 and this one is one of the more complex ones, 189 00:10:27.690 --> 00:10:28.740 or I would even say 190 00:10:28.740 --> 00:10:31.440 really the most difficult of all of them. 191 00:10:31.440 --> 00:10:33.000 So if you didn't get this one right, 192 00:10:33.000 --> 00:10:35.190 that's really no problem. 193 00:10:35.190 --> 00:10:39.600 But anyway, the instruction reads, many dogs like to swim, 194 00:10:39.600 --> 00:10:42.210 or actually many breeds like to swim. 195 00:10:42.210 --> 00:10:46.260 And now here the idea is to store all the other activities 196 00:10:46.260 --> 00:10:49.080 that these breeds like to do. 197 00:10:49.080 --> 00:10:52.110 So the ones that like to swim in a unique array 198 00:10:52.110 --> 00:10:54.063 called swimming adjacent. 199 00:10:55.050 --> 00:10:56.400 So this sounds a bit complex. 200 00:10:56.400 --> 00:10:58.260 So let's go here. 201 00:10:58.260 --> 00:11:01.830 So let's see all the activities that have swimming. 202 00:11:01.830 --> 00:11:03.273 So this one here. 203 00:11:04.410 --> 00:11:06.570 So this one, this one, and this one. 204 00:11:06.570 --> 00:11:09.570 These are the three breeds that like to swim. 205 00:11:09.570 --> 00:11:13.290 And so now the idea is to find the adjacent activities, 206 00:11:13.290 --> 00:11:17.040 which are the activities that these dogs also like to do. 207 00:11:17.040 --> 00:11:18.300 So that's fetching. 208 00:11:18.300 --> 00:11:19.770 So fetch. 209 00:11:19.770 --> 00:11:21.000 Here again, fetch, 210 00:11:21.000 --> 00:11:23.520 and then running and agility. 211 00:11:23.520 --> 00:11:25.830 So this is gonna be our result. 212 00:11:25.830 --> 00:11:29.253 And so let's now try to see how we can achieve that. 213 00:11:30.720 --> 00:11:33.840 So let's call this here swimmingAdjacent 214 00:11:33.840 --> 00:11:35.740 as the instruction sets 215 00:11:36.990 --> 00:11:39.585 and so breeds. 216 00:11:39.585 --> 00:11:42.120 And then the first thing to do is probably 217 00:11:42.120 --> 00:11:45.900 to find all of the breeds that like to swim. 218 00:11:45.900 --> 00:11:47.313 So that makes sense, right? 219 00:11:48.180 --> 00:11:50.523 So we use a filter for that. 220 00:11:51.990 --> 00:11:56.990 So breed, and then we say breed.activities.includes again, 221 00:12:02.640 --> 00:12:03.990 swimming. 222 00:12:03.990 --> 00:12:06.270 So let's see if we're underwrite. 223 00:12:06.270 --> 00:12:09.447 Trek with console.logs(swimmingAdjacent), 224 00:12:13.950 --> 00:12:14.783 and 225 00:12:17.010 --> 00:12:20.130 yeah, so these are exactly the three breeds 226 00:12:20.130 --> 00:12:23.250 that we manually identified earlier. 227 00:12:23.250 --> 00:12:26.280 Now what we need to do next is to get these activities 228 00:12:26.280 --> 00:12:29.040 out of these objects. 229 00:12:29.040 --> 00:12:30.780 So basically having an array 230 00:12:30.780 --> 00:12:34.410 where these activities are then stored. 231 00:12:34.410 --> 00:12:38.313 And so this means that we just use a map. 232 00:12:39.180 --> 00:12:42.630 So again, breed. 233 00:12:42.630 --> 00:12:46.160 And then here, we just want to get the breed.activities. 234 00:12:49.680 --> 00:12:51.990 And so this looks a lot better, 235 00:12:51.990 --> 00:12:55.740 but just like before, we don't want an array of arrays, 236 00:12:55.740 --> 00:12:58.920 but we want all of these activities in one array. 237 00:12:58.920 --> 00:13:01.770 So we could just chain on a flat, 238 00:13:01.770 --> 00:13:03.940 but instead, let's use a flatMap. 239 00:13:06.930 --> 00:13:10.830 And nice, this is starting to look really good. 240 00:13:10.830 --> 00:13:14.433 Let's just now actually make them unique. 241 00:13:15.270 --> 00:13:18.180 So basically doing the same thing as before, 242 00:13:18.180 --> 00:13:19.720 wrapping all this in a set 243 00:13:20.880 --> 00:13:23.280 and in an array. 244 00:13:23.280 --> 00:13:25.023 So creating a new array, 245 00:13:26.040 --> 00:13:30.750 which will be actually need to keep this selected. 246 00:13:30.750 --> 00:13:35.343 So parenthesis and then new Set. 247 00:13:36.720 --> 00:13:38.070 And actually that's not correct 248 00:13:38.070 --> 00:13:40.320 because now we need to spread these elements 249 00:13:40.320 --> 00:13:42.390 into this newly created array. 250 00:13:42.390 --> 00:13:43.770 And beautiful. 251 00:13:43.770 --> 00:13:47.280 Now we have these adjacent activities 252 00:13:47.280 --> 00:13:52.280 that we identified earlier up here, right? 253 00:13:52.890 --> 00:13:54.930 So that was exactly what we have there. 254 00:13:54.930 --> 00:13:55.923 Fetching, 255 00:13:56.970 --> 00:14:00.540 and fetching again, and running and agility. 256 00:14:00.540 --> 00:14:02.010 Let's just remove the swimming here 257 00:14:02.010 --> 00:14:04.380 because that's not really adjacent. 258 00:14:04.380 --> 00:14:07.380 We want the other activities. 259 00:14:07.380 --> 00:14:08.550 But that's very easy. 260 00:14:08.550 --> 00:14:11.883 We just do another filter in the end. 261 00:14:13.350 --> 00:14:16.920 So at this point, these are called activities. 262 00:14:16.920 --> 00:14:19.323 So each element of the array is now an activity. 263 00:14:21.360 --> 00:14:26.250 And so let's say activity should be different from swimming. 264 00:14:30.150 --> 00:14:31.350 And just like this, 265 00:14:31.350 --> 00:14:35.373 we solved this challenge or this task number five. 266 00:14:36.600 --> 00:14:38.550 So this looks pretty complex here, 267 00:14:38.550 --> 00:14:40.710 but if you build it step by step 268 00:14:40.710 --> 00:14:44.550 like we did here, also while looking at the data structure 269 00:14:44.550 --> 00:14:46.020 that we're working with, 270 00:14:46.020 --> 00:14:48.243 it becomes a little bit easier at least. 271 00:14:50.100 --> 00:14:52.470 So let's move on to number six now, 272 00:14:52.470 --> 00:14:54.540 which is just a simple question. 273 00:14:54.540 --> 00:14:57.030 Do all the breeds have an average weight 274 00:14:57.030 --> 00:14:59.250 of 10 kilos or more? 275 00:14:59.250 --> 00:15:03.120 Simply log to the console whether this is true or false. 276 00:15:03.120 --> 00:15:07.110 Now, since we need a Boolean value here, so a true or false, 277 00:15:07.110 --> 00:15:09.840 some great candidates for the method 278 00:15:09.840 --> 00:15:14.490 that we need here are the every and the some methods. 279 00:15:14.490 --> 00:15:15.570 There are some other methods 280 00:15:15.570 --> 00:15:19.050 that also give you a Boolean like the includes method 281 00:15:19.050 --> 00:15:21.360 that we have used here a few times, 282 00:15:21.360 --> 00:15:24.930 but this one doesn't make so much sense in this case. 283 00:15:24.930 --> 00:15:27.000 And by the way, later in the section, 284 00:15:27.000 --> 00:15:29.010 there is a very handy lecture 285 00:15:29.010 --> 00:15:32.190 which summarizes all of these different array methods. 286 00:15:32.190 --> 00:15:35.490 In fact, I think it's 30 array methods. 287 00:15:35.490 --> 00:15:39.360 And there you will find basically a small decision framework 288 00:15:39.360 --> 00:15:41.610 where you can more easily find out 289 00:15:41.610 --> 00:15:45.930 which of the array methods you should use in each situation. 290 00:15:45.930 --> 00:15:49.260 But now back to this question right here, 291 00:15:49.260 --> 00:15:52.320 the question asks whether all the breeds 292 00:15:52.320 --> 00:15:55.140 have some average weight, right? 293 00:15:55.140 --> 00:15:57.870 And so whenever you hear this all, 294 00:15:57.870 --> 00:16:02.870 then the method to use is probably the every method. 295 00:16:03.240 --> 00:16:06.750 So let's just log to the console here. 296 00:16:06.750 --> 00:16:09.840 And so then breeds. 297 00:16:09.840 --> 00:16:12.060 And as I just mentioned every. 298 00:16:12.060 --> 00:16:14.850 And so, every only becomes true 299 00:16:14.850 --> 00:16:18.660 if all of the elements in the array satisfy the condition 300 00:16:18.660 --> 00:16:21.030 that we're gonna specify here in the callback. 301 00:16:21.030 --> 00:16:25.140 So if the callback is true for every single element, 302 00:16:25.140 --> 00:16:29.040 then the every method will also return true. 303 00:16:29.040 --> 00:16:30.630 While in the some method, 304 00:16:30.630 --> 00:16:34.920 only one of the elements in the array needs to be true 305 00:16:34.920 --> 00:16:38.880 in order for the whole expression to become true basically. 306 00:16:38.880 --> 00:16:41.790 So in order for some to become true. 307 00:16:41.790 --> 00:16:42.663 But anyway, 308 00:16:44.310 --> 00:16:47.793 once again, each element in this array is a breed. 309 00:16:48.630 --> 00:16:53.630 And so we're asking whether the average weight 310 00:16:54.390 --> 00:16:57.060 is 10 kilos or more. 311 00:16:57.060 --> 00:16:59.523 So average weight, right? 312 00:17:00.990 --> 00:17:03.150 Yeah, so all of these have an average weight 313 00:17:03.150 --> 00:17:06.600 and we're now gonna check whether it is greater than 10 314 00:17:06.600 --> 00:17:07.623 for all of them. 315 00:17:08.610 --> 00:17:12.750 So we can actually see that this is going to be true, right? 316 00:17:12.750 --> 00:17:14.680 Because the one that has 317 00:17:17.340 --> 00:17:19.953 the less a weight is that beagle. 318 00:17:20.940 --> 00:17:23.913 So let's see, greater than 10. 319 00:17:24.900 --> 00:17:27.780 And indeed it is true. 320 00:17:27.780 --> 00:17:29.793 Let's just change something here. 321 00:17:31.380 --> 00:17:34.410 Let's make this just one kilo. 322 00:17:34.410 --> 00:17:35.940 And so now it is false. 323 00:17:35.940 --> 00:17:40.530 So if just one of all of these elements here 324 00:17:40.530 --> 00:17:42.510 does not satisfy the condition, 325 00:17:42.510 --> 00:17:44.580 then the whole thing becomes false. 326 00:17:44.580 --> 00:17:47.820 So it's a little bit like the AND operator, 327 00:17:47.820 --> 00:17:51.363 but applied to all of these different array elements. 328 00:17:54.180 --> 00:17:57.963 While the some method is more like the OR operator. 329 00:17:59.040 --> 00:18:01.350 And speaking of the some method, 330 00:18:01.350 --> 00:18:05.670 I think this one is gonna be handy in the next task. 331 00:18:05.670 --> 00:18:07.650 So task number seven says, 332 00:18:07.650 --> 00:18:10.860 are there any breeds that are active? 333 00:18:10.860 --> 00:18:14.220 And active simply means that this dog has three 334 00:18:14.220 --> 00:18:15.543 or more activities. 335 00:18:20.340 --> 00:18:23.580 So three or more activities. 336 00:18:23.580 --> 00:18:24.993 Let's see if there are any. 337 00:18:26.340 --> 00:18:28.170 And actually there are not. 338 00:18:28.170 --> 00:18:29.943 So this is gonna be false. 339 00:18:30.840 --> 00:18:32.400 So let's check, 340 00:18:32.400 --> 00:18:35.283 breeds.some, 341 00:18:36.240 --> 00:18:37.380 breed 342 00:18:37.380 --> 00:18:42.380 and then breed.activities.length greater than three. 343 00:18:48.450 --> 00:18:52.503 And here it is laying more like this. 344 00:18:53.610 --> 00:18:56.070 And so now we get a problem here, 345 00:18:56.070 --> 00:18:59.850 and that's because here it is breed and not breeds. 346 00:18:59.850 --> 00:19:02.340 And so indeed it is false. 347 00:19:02.340 --> 00:19:03.460 Now, actually, I think 348 00:19:05.100 --> 00:19:08.433 the active means that there's three or more. 349 00:19:09.540 --> 00:19:11.550 So it is not more than three, 350 00:19:11.550 --> 00:19:14.553 but actually more or equal three. 351 00:19:15.870 --> 00:19:16.990 So 352 00:19:18.390 --> 00:19:20.940 greater or equal. 353 00:19:20.940 --> 00:19:22.830 And yeah, now that is true. 354 00:19:22.830 --> 00:19:25.260 And again, that's because this some method here 355 00:19:25.260 --> 00:19:27.570 is a little bit like the OR operator. 356 00:19:27.570 --> 00:19:30.720 So it is enough for one of the array elements 357 00:19:30.720 --> 00:19:33.300 to return true here in this callback 358 00:19:33.300 --> 00:19:35.853 for the whole thing to become true as well. 359 00:19:37.080 --> 00:19:40.560 And indeed, there are actually two dogs in this condition. 360 00:19:40.560 --> 00:19:42.933 These two have three activities each. 361 00:19:43.920 --> 00:19:44.820 Great. 362 00:19:44.820 --> 00:19:48.540 So as I mentioned, this is actually a long one. 363 00:19:48.540 --> 00:19:51.360 So this video is already running for some time, 364 00:19:51.360 --> 00:19:53.910 but we still have a bonus question to answer, 365 00:19:53.910 --> 00:19:57.090 which I believe was also pretty difficult. 366 00:19:57.090 --> 00:19:58.410 So let's see. 367 00:19:58.410 --> 00:20:00.720 The task in this case is to find out 368 00:20:00.720 --> 00:20:04.500 what is the average weight of the heaviest breed 369 00:20:04.500 --> 00:20:06.450 that likes to fetch. 370 00:20:06.450 --> 00:20:10.020 So let's once again go to our data structure. 371 00:20:10.020 --> 00:20:13.170 And so basically we're gonna select all of the breeds 372 00:20:13.170 --> 00:20:15.300 that like to fetch, 373 00:20:15.300 --> 00:20:19.170 and then we just want to find the heaviest of all of them. 374 00:20:19.170 --> 00:20:23.313 So the one which has the largest average weight. 375 00:20:26.220 --> 00:20:30.180 So deconstructing a problem into these multiple parts 376 00:20:30.180 --> 00:20:34.110 always makes it a lot easier to understand 377 00:20:34.110 --> 00:20:35.850 what we need to do. 378 00:20:35.850 --> 00:20:39.690 So let's first of all, find out these different breeds 379 00:20:39.690 --> 00:20:41.250 that like to fetch. 380 00:20:41.250 --> 00:20:44.520 Let's call them the fetch breeds. 381 00:20:44.520 --> 00:20:48.690 And this is pretty easy, 382 00:20:48.690 --> 00:20:49.650 this part. 383 00:20:49.650 --> 00:20:51.663 So we've done this many times before. 384 00:20:53.040 --> 00:20:54.540 So here the breed 385 00:20:54.540 --> 00:20:59.433 and then breeds.activities.includes, 386 00:21:00.630 --> 00:21:01.950 and then fetch. 387 00:21:01.950 --> 00:21:03.633 Let's see what we got. 388 00:21:08.760 --> 00:21:13.230 And indeed, these are the five that we identified earlier. 389 00:21:13.230 --> 00:21:17.703 And so now we need to in the next step get their weights. 390 00:21:19.260 --> 00:21:23.700 So once again, for that, we use the map method. 391 00:21:23.700 --> 00:21:27.990 So breed, and then we just get breed.averageWeight, 392 00:21:30.150 --> 00:21:32.000 and then we get all of their weights. 393 00:21:33.750 --> 00:21:36.420 Let's actually call this here, breed... 394 00:21:36.420 --> 00:21:37.413 Or fetchWeights, 395 00:21:40.500 --> 00:21:42.300 and here as well. 396 00:21:42.300 --> 00:21:43.950 That makes a bit more sense. 397 00:21:43.950 --> 00:21:45.420 And now all we need to do 398 00:21:45.420 --> 00:21:48.780 is to find the largest value of these. 399 00:21:48.780 --> 00:21:51.330 And for that, we actually have a hint, 400 00:21:51.330 --> 00:21:54.420 which is to use the Math.max method 401 00:21:54.420 --> 00:21:57.360 along with the spread operator. 402 00:21:57.360 --> 00:21:59.253 So let's see what that is all about. 403 00:22:00.090 --> 00:22:02.573 So const, and then let's call this one heaviestFetchBreed. 404 00:22:10.020 --> 00:22:14.647 And so as I just mentioned, let's try to use Math.max, 405 00:22:16.110 --> 00:22:20.010 and then pass in the fetchWeights. 406 00:22:20.010 --> 00:22:23.960 And here, then let's just only... 407 00:22:24.990 --> 00:22:29.250 Well actually, let's keep both of them here 408 00:22:29.250 --> 00:22:32.373 just so we can see that the result is correct, 409 00:22:33.600 --> 00:22:36.660 but actually we get a not a number. 410 00:22:36.660 --> 00:22:40.950 And so that's because this Math.max function right here 411 00:22:40.950 --> 00:22:43.170 does not simply accept an array 412 00:22:43.170 --> 00:22:44.880 and will give us the largest value. 413 00:22:44.880 --> 00:22:46.530 That's not how it works. 414 00:22:46.530 --> 00:22:49.860 The way this works is that we give it multiple values 415 00:22:49.860 --> 00:22:53.040 and it'll simply give us the largest of them. 416 00:22:53.040 --> 00:22:54.900 So we've done this before. 417 00:22:54.900 --> 00:22:56.730 Let me just demonstrate that to you 418 00:22:56.730 --> 00:23:00.510 so we can pass as many values as we want here. 419 00:23:00.510 --> 00:23:03.420 And of all of these arguments that we pass it, 420 00:23:03.420 --> 00:23:05.733 it'll just give us the largest ones. 421 00:23:06.870 --> 00:23:08.490 So how do we do this? 422 00:23:08.490 --> 00:23:11.820 Basically, how do we take the values out of the array? 423 00:23:11.820 --> 00:23:15.540 Well, that's where this spread operator comes into play, 424 00:23:15.540 --> 00:23:19.710 because what this operator does is basically just like this, 425 00:23:19.710 --> 00:23:23.100 it takes the values here and places them. 426 00:23:23.100 --> 00:23:24.750 Well, now it's gone, 427 00:23:24.750 --> 00:23:26.340 but it places them right there 428 00:23:26.340 --> 00:23:31.340 into this Math.max function here as arguments in this case. 429 00:23:32.190 --> 00:23:37.113 And so now indeed, we get 32 as the largest of these values. 430 00:23:38.190 --> 00:23:39.023 Great. 431 00:23:39.023 --> 00:23:43.290 So this was a lot of work, but I hope also a lot of fun. 432 00:23:43.290 --> 00:23:45.750 I really liked designing this challenge for you 433 00:23:45.750 --> 00:23:47.970 and now also solving it. 434 00:23:47.970 --> 00:23:51.480 So a lot of different methods we used here. 435 00:23:51.480 --> 00:23:54.870 And yeah, really nice challenge here as well. 436 00:23:54.870 --> 00:23:56.520 So I hope you had some fun, 437 00:23:56.520 --> 00:23:58.290 and I see you in the next video 438 00:23:58.290 --> 00:23:59.820 where we keep working 439 00:23:59.820 --> 00:24:02.043 with some very important array methods.