1 00:00:01,300 --> 00:00:02,210 In the past, 2 00:00:02,210 --> 00:00:04,740 JavaScript has always had very little 3 00:00:04,740 --> 00:00:06,900 built-in data structures. 4 00:00:06,900 --> 00:00:10,600 So basically, we only had objects and arrays. 5 00:00:10,600 --> 00:00:13,650 But in ESX, two more data structures 6 00:00:13,650 --> 00:00:15,570 were finally introduced. 7 00:00:15,570 --> 00:00:18,550 And that are. sets and maps. 8 00:00:18,550 --> 00:00:21,350 So these are pretty common data structures 9 00:00:21,350 --> 00:00:24,660 that already exists in other programming languages, 10 00:00:24,660 --> 00:00:27,860 and now, they also exist in JavaScript. 11 00:00:27,860 --> 00:00:31,453 So in this lecture, let's learn all about sets. 12 00:00:33,160 --> 00:00:36,270 And a set is basically just a collection 13 00:00:36,270 --> 00:00:38,330 of unique values. 14 00:00:38,330 --> 00:00:42,200 So that means that a set can never have any duplicates. 15 00:00:42,200 --> 00:00:44,180 And that property makes them useful 16 00:00:44,180 --> 00:00:46,400 in certain situations. 17 00:00:46,400 --> 00:00:48,193 So let's create a new set here. 18 00:00:50,220 --> 00:00:51,807 Let's call it ordersSet. 19 00:00:57,257 --> 00:01:00,280 Okay. So again, to create a new set, 20 00:01:00,280 --> 00:01:02,310 we write new set 21 00:01:02,310 --> 00:01:05,060 and then here, we need to pass in an iterable. 22 00:01:05,060 --> 00:01:08,620 And the most common iterable here is an array. 23 00:01:08,620 --> 00:01:10,260 So let's create an array 24 00:01:10,260 --> 00:01:12,713 with a couple of strings now. 25 00:01:13,760 --> 00:01:16,483 Let's say pasta, pizza, 26 00:01:18,810 --> 00:01:20,073 then pizza again, 27 00:01:23,000 --> 00:01:27,163 then risotto. Let's put another pasta, 28 00:01:29,440 --> 00:01:31,033 and another pizza. 29 00:01:33,080 --> 00:01:36,140 Okay. So six strings. 30 00:01:36,140 --> 00:01:39,790 But of course, they could be different data types in here. 31 00:01:39,790 --> 00:01:43,050 So set can of course hold mixed data types. 32 00:01:43,050 --> 00:01:45,380 That's not a problem at all. 33 00:01:45,380 --> 00:01:48,483 Now, here we clearly see some duplicate strings. 34 00:01:49,560 --> 00:01:50,520 So what do you think 35 00:01:50,520 --> 00:01:52,557 that this set will look like? 36 00:01:52,557 --> 00:01:54,680 And now that we created it, 37 00:01:54,680 --> 00:01:56,380 and when we log it to the console? 38 00:01:57,930 --> 00:01:59,880 Well, we get a set. 39 00:01:59,880 --> 00:02:03,060 Here, we can see it has a size of three. 40 00:02:03,060 --> 00:02:04,860 And the only values that are in there 41 00:02:04,860 --> 00:02:08,020 are pasta, pizza and risotto. 42 00:02:08,020 --> 00:02:12,360 So, that's right. All the duplicates are actually gone. 43 00:02:12,360 --> 00:02:15,110 Now, also we can see that a set 44 00:02:15,110 --> 00:02:18,980 kind of looks similar to an array, right. 45 00:02:18,980 --> 00:02:21,390 So there are no key value pairs, 46 00:02:21,390 --> 00:02:24,680 it's just a bunch of values grouped together, 47 00:02:24,680 --> 00:02:26,810 in this case into a set. 48 00:02:26,810 --> 00:02:30,880 And just like arrays, sets are also iterables. 49 00:02:30,880 --> 00:02:33,800 Okay. Now, of course a set 50 00:02:33,800 --> 00:02:36,350 is still very different from an array. 51 00:02:36,350 --> 00:02:39,790 So first, because its elements are unique. 52 00:02:39,790 --> 00:02:41,610 And second, because the order 53 00:02:41,610 --> 00:02:45,410 of elements in the set is irrelevant. 54 00:02:45,410 --> 00:02:47,603 And we will see why in a second. 55 00:02:48,700 --> 00:02:51,410 But anyway, keep in mind that strings 56 00:02:51,410 --> 00:02:52,823 are also iterables. 57 00:02:53,690 --> 00:02:55,073 So we can do this. 58 00:02:58,180 --> 00:03:00,523 So we can pass in a string. 59 00:03:02,460 --> 00:03:03,970 And so now we get a set 60 00:03:03,970 --> 00:03:06,060 with these five elements. 61 00:03:06,060 --> 00:03:08,850 So, and that's the five components basically 62 00:03:08,850 --> 00:03:11,943 of this iterable, which is the string. 63 00:03:13,250 --> 00:03:16,510 And of course, the set could also be empty, 64 00:03:16,510 --> 00:03:17,463 just like this. 65 00:03:18,790 --> 00:03:21,090 All right. And now let's learn how 66 00:03:21,090 --> 00:03:23,300 to actually work with sets. 67 00:03:23,300 --> 00:03:26,433 So first off, we can get the size of a set. 68 00:03:27,330 --> 00:03:30,570 So orderSet.size. 69 00:03:30,570 --> 00:03:32,380 And so that is three. 70 00:03:32,380 --> 00:03:34,260 And so in this particular example, 71 00:03:34,260 --> 00:03:37,260 this might be useful for the chef of our kitchen 72 00:03:37,260 --> 00:03:39,440 to know how many different meals 73 00:03:39,440 --> 00:03:40,913 are going to be cooked here. 74 00:03:42,530 --> 00:03:44,980 Right. So if this array here is an array 75 00:03:44,980 --> 00:03:46,840 of all the orders, 76 00:03:46,840 --> 00:03:48,500 then the set of these orders 77 00:03:48,500 --> 00:03:50,760 are simply the unique different meals 78 00:03:50,760 --> 00:03:52,210 that are gonna be cooked. 79 00:03:52,210 --> 00:03:53,530 And then the size 80 00:03:53,530 --> 00:03:56,220 is how many different meals will be cooked? 81 00:03:56,220 --> 00:03:59,460 And just note, how it is actually called size 82 00:03:59,460 --> 00:04:00,580 and to not length 83 00:04:00,580 --> 00:04:02,460 like it is in arrays. 84 00:04:02,460 --> 00:04:04,283 So don't make that confusion. 85 00:04:05,130 --> 00:04:09,523 Next, we can check if a certain element is in a set. 86 00:04:11,040 --> 00:04:14,380 So orderset.has. 87 00:04:14,380 --> 00:04:17,330 And so this is actually a method. 88 00:04:17,330 --> 00:04:20,350 And so let's check if pizza is in there. 89 00:04:20,350 --> 00:04:24,520 And let's check if bread is in there. 90 00:04:24,520 --> 00:04:26,180 So true and false. 91 00:04:26,180 --> 00:04:29,490 And that's exactly as we expect it. 92 00:04:29,490 --> 00:04:32,700 And so, comparing again two arrays, 93 00:04:32,700 --> 00:04:34,880 this has method is similar 94 00:04:34,880 --> 00:04:38,070 to the includes method in arrays. 95 00:04:38,070 --> 00:04:40,410 Right. Next step, 96 00:04:40,410 --> 00:04:43,703 we can also add new elements to a set. 97 00:04:44,840 --> 00:04:46,073 So orderSet. 98 00:04:49,220 --> 00:04:52,463 So let's say that now someone ordered garlic bread. 99 00:04:56,790 --> 00:05:00,160 And let's say that is actually happened twice. 100 00:05:00,160 --> 00:05:01,470 So, what do you think 101 00:05:01,470 --> 00:05:03,363 that the set will look like now? 102 00:05:06,480 --> 00:05:07,313 So orderSet. 103 00:05:08,710 --> 00:05:12,360 And so the garlic bread got added. 104 00:05:12,360 --> 00:05:14,800 But only, of course, one of them, 105 00:05:14,800 --> 00:05:18,070 because again, the set has to be unique. 106 00:05:18,070 --> 00:05:20,943 And so the second one was basically ignored. 107 00:05:22,920 --> 00:05:26,080 Finally, we can also delete elements. 108 00:05:26,080 --> 00:05:28,513 So let's do that before the log. 109 00:05:29,820 --> 00:05:32,203 So orderSet.delete. 110 00:05:33,090 --> 00:05:34,450 So all of these method names 111 00:05:34,450 --> 00:05:36,390 are very straightforward. 112 00:05:36,390 --> 00:05:39,863 And that's because this is such a modern feature. 113 00:05:41,810 --> 00:05:43,740 So the modern stuff really has 114 00:05:43,740 --> 00:05:46,900 this more straightforward names, 115 00:05:46,900 --> 00:05:48,920 and a different way of working 116 00:05:48,920 --> 00:05:50,363 with the data structures. 117 00:05:51,710 --> 00:05:53,070 So we have risotto here. 118 00:05:53,070 --> 00:05:55,160 And so now here we are deleting it. 119 00:05:55,160 --> 00:05:57,840 And so Indeed, it is now gone 120 00:05:57,840 --> 00:05:59,590 from the set. 121 00:05:59,590 --> 00:06:01,230 So really, really easy. 122 00:06:01,230 --> 00:06:03,920 And in arrays, there is actually no method 123 00:06:03,920 --> 00:06:06,050 that is this simple. 124 00:06:06,050 --> 00:06:08,350 We will see how to delete elements 125 00:06:08,350 --> 00:06:09,710 from arrays later. 126 00:06:09,710 --> 00:06:13,130 But I can tell you that it's a little bit more complex. 127 00:06:13,130 --> 00:06:15,500 Okay, and that's actually it. 128 00:06:15,500 --> 00:06:17,070 But now you might ask, 129 00:06:17,070 --> 00:06:21,240 how do we actually retrieve values out of a set? 130 00:06:21,240 --> 00:06:23,080 Can we maybe use an index, 131 00:06:23,080 --> 00:06:25,020 like in a race? 132 00:06:25,020 --> 00:06:28,433 So doing something like, maybe like this here? 133 00:06:29,930 --> 00:06:33,690 And the answer, as we will see is no. 134 00:06:33,690 --> 00:06:35,230 So this doesn't work, 135 00:06:35,230 --> 00:06:36,890 it gives us undefined, 136 00:06:36,890 --> 00:06:38,833 no matter what number we put here. 137 00:06:40,710 --> 00:06:42,340 All right. And that is 138 00:06:42,340 --> 00:06:45,700 because in sets there are actually no indexes. 139 00:06:45,700 --> 00:06:48,210 And in fact, there is no way 140 00:06:48,210 --> 00:06:51,000 of getting values out of a set. 141 00:06:51,000 --> 00:06:52,740 And if we think about this, 142 00:06:52,740 --> 00:06:54,700 then it makes sense. 143 00:06:54,700 --> 00:06:57,950 So there's really no need for getting data out 144 00:06:57,950 --> 00:07:02,240 of a set. That's because if all values are unique, 145 00:07:02,240 --> 00:07:04,690 and if their order does not matter, 146 00:07:04,690 --> 00:07:06,300 then there is no point 147 00:07:06,300 --> 00:07:08,659 of retrieving values out of a set. 148 00:07:08,659 --> 00:07:10,240 All we need to know 149 00:07:10,240 --> 00:07:11,640 is whether a certain value 150 00:07:11,640 --> 00:07:13,560 is in the set or not. 151 00:07:13,560 --> 00:07:16,810 And that's why we have the has method. 152 00:07:16,810 --> 00:07:19,810 If your goal is to actually store values in order 153 00:07:19,810 --> 00:07:21,023 and then retrieve it, 154 00:07:21,023 --> 00:07:24,420 then the best use case, is to just use an array. 155 00:07:24,420 --> 00:07:26,510 You wouldn't use a set for that. 156 00:07:26,510 --> 00:07:28,480 And so again, there's no need 157 00:07:28,480 --> 00:07:30,890 for getting values out of a set, 158 00:07:30,890 --> 00:07:34,080 because if you need it, then you will just use an array. 159 00:07:34,080 --> 00:07:38,060 Finally, there is actually one more method here 160 00:07:39,010 --> 00:07:40,410 but it's not that important. 161 00:07:40,410 --> 00:07:41,810 All we can use it for is 162 00:07:41,810 --> 00:07:45,900 to basically delete all of the elements 163 00:07:45,900 --> 00:07:47,430 of the set. 164 00:07:47,430 --> 00:07:51,550 And so we see that now it is empty, right. 165 00:07:51,550 --> 00:07:53,350 But let's put that back, 166 00:07:53,350 --> 00:07:56,520 so that we can work some more with a set. 167 00:07:56,520 --> 00:07:59,380 So as I said, in the beginning, 168 00:07:59,380 --> 00:08:01,720 sets are also iterables. 169 00:08:01,720 --> 00:08:04,283 And therefore, we can loop over them. 170 00:08:05,980 --> 00:08:08,320 So let's say, order 171 00:08:08,320 --> 00:08:09,783 from ordersSet 172 00:08:12,130 --> 00:08:13,410 and not from... 173 00:08:13,410 --> 00:08:16,950 It is off, obviously. 174 00:08:16,950 --> 00:08:18,953 And then we can just lock the order. 175 00:08:20,510 --> 00:08:22,543 And indeed, here they are. 176 00:08:23,950 --> 00:08:25,750 So looping is possible, 177 00:08:25,750 --> 00:08:28,280 just like in any other iterable. 178 00:08:28,280 --> 00:08:32,870 All right, so now that we know how to work with sets, 179 00:08:32,870 --> 00:08:36,880 let's see a big use case for them right now. 180 00:08:36,880 --> 00:08:38,750 So in a normal code base, 181 00:08:38,750 --> 00:08:41,580 the main use case of sets is actually 182 00:08:41,580 --> 00:08:44,123 to remove duplicate values of arrays. 183 00:08:45,500 --> 00:08:47,980 So let's just write that here. 184 00:08:47,980 --> 00:08:51,860 Example. So let's say that we have an array 185 00:08:51,860 --> 00:08:53,500 in our restaurant, 186 00:08:53,500 --> 00:08:56,993 which contains the staff of our restaurant. 187 00:08:58,580 --> 00:09:00,370 Let's say, we have one person 188 00:09:00,370 --> 00:09:01,483 that is the waiter, 189 00:09:02,350 --> 00:09:03,923 one person, that is the chef, 190 00:09:04,980 --> 00:09:07,490 another person, that is a waiter, 191 00:09:07,490 --> 00:09:09,893 then we have also a manager, 192 00:09:11,290 --> 00:09:13,580 then we have another person 193 00:09:13,580 --> 00:09:15,610 that is a chef also, 194 00:09:15,610 --> 00:09:16,713 and another waiter. 195 00:09:18,190 --> 00:09:19,240 So that's an array 196 00:09:19,240 --> 00:09:22,820 of all our staff in the restaurant. 197 00:09:22,820 --> 00:09:24,840 But now let's say that for some reason, 198 00:09:24,840 --> 00:09:27,310 we are interested in knowing only 199 00:09:27,310 --> 00:09:30,950 which different positions there are in our restaurant. 200 00:09:30,950 --> 00:09:32,340 Or in other words, 201 00:09:32,340 --> 00:09:34,160 we would basically like 202 00:09:34,160 --> 00:09:38,260 to have a unique array of this, right? 203 00:09:38,260 --> 00:09:41,410 So this array without all the duplicates 204 00:09:41,410 --> 00:09:43,150 that will solve the problem. 205 00:09:43,150 --> 00:09:46,430 So let's create a set for that. 206 00:09:46,430 --> 00:09:47,763 Easy enough, right? 207 00:09:50,150 --> 00:09:53,540 So staff, unique, 208 00:09:53,540 --> 00:09:57,110 equals, new, set, 209 00:09:57,110 --> 00:09:58,180 and then the iterable 210 00:09:58,180 --> 00:10:00,980 that we need to pass in, here's the staff 211 00:10:00,980 --> 00:10:03,313 because an array is already an iterable. 212 00:10:04,870 --> 00:10:07,730 Now, this is not yet the end of the solution, 213 00:10:07,730 --> 00:10:10,093 but let's take a look at it for now. 214 00:10:11,120 --> 00:10:16,120 And, of course, it needs to be staff, unique. 215 00:10:16,180 --> 00:10:19,660 And so, yes. So we have a set now 216 00:10:19,660 --> 00:10:22,530 with waiter, chef and manager. 217 00:10:22,530 --> 00:10:25,210 So the three unique positions. 218 00:10:25,210 --> 00:10:26,720 But now we actually want this 219 00:10:26,720 --> 00:10:28,610 to be an array. 220 00:10:28,610 --> 00:10:30,220 But the conversion from a set 221 00:10:30,220 --> 00:10:32,400 to an array is pretty easy, 222 00:10:32,400 --> 00:10:34,690 because they're both iterables. 223 00:10:34,690 --> 00:10:36,490 So remember from earlier 224 00:10:36,490 --> 00:10:38,290 that the spread operator works 225 00:10:38,290 --> 00:10:40,720 on all iterables. Right? 226 00:10:40,720 --> 00:10:43,180 So that includes sets. 227 00:10:43,180 --> 00:10:47,860 And so we can now create an array around this basically. 228 00:10:47,860 --> 00:10:49,440 And then we can unpack 229 00:10:49,440 --> 00:10:52,510 this entire set here 230 00:10:52,510 --> 00:10:54,560 using the spread operator, 231 00:10:54,560 --> 00:10:56,730 and then these elements will be put 232 00:10:56,730 --> 00:11:00,413 into the newly constructed array. Okay. 233 00:11:01,310 --> 00:11:03,560 And so Indeed, we now end up 234 00:11:03,560 --> 00:11:06,040 with a new array. Okay. 235 00:11:06,040 --> 00:11:08,860 So the spread operator here works just like 236 00:11:08,860 --> 00:11:12,430 on an array. It works really exactly the same. 237 00:11:12,430 --> 00:11:15,220 So it takes all the elements out of the iterable 238 00:11:15,220 --> 00:11:17,790 and essentially writes them here, 239 00:11:17,790 --> 00:11:20,780 like comma separated, right. 240 00:11:20,780 --> 00:11:23,030 Now, if we only wanted to know 241 00:11:23,030 --> 00:11:25,560 how many different positions there are, 242 00:11:25,560 --> 00:11:27,360 then the size property 243 00:11:27,360 --> 00:11:28,513 is very useful. 244 00:11:29,690 --> 00:11:31,293 So all you would have to do, 245 00:11:32,230 --> 00:11:34,420 even though this looks a little bit weird, 246 00:11:34,420 --> 00:11:35,713 would be to say, 247 00:11:37,580 --> 00:11:41,653 new set, then with the array, 248 00:11:42,970 --> 00:11:43,923 and then .size. 249 00:11:46,380 --> 00:11:47,370 And that's it. 250 00:11:47,370 --> 00:11:48,770 And then we wouldn't even need 251 00:11:48,770 --> 00:11:52,150 to have to create the array at all. 252 00:11:52,150 --> 00:11:55,870 So if we didn't need the unique array. 253 00:11:55,870 --> 00:11:57,840 So if all we had was this, 254 00:11:57,840 --> 00:12:01,000 and we wanted to know how many unique positions there are, 255 00:12:01,000 --> 00:12:03,280 then this year would be the way to go. 256 00:12:03,280 --> 00:12:06,260 And the same could even be done with counting, 257 00:12:06,260 --> 00:12:10,720 how many different letters there are in a string, right. 258 00:12:10,720 --> 00:12:13,130 Because an iterable, 259 00:12:13,130 --> 00:12:15,553 or actually a string is also an iterable. 260 00:12:17,970 --> 00:12:20,580 So let's see how many different letters there 261 00:12:20,580 --> 00:12:21,593 are in my name. 262 00:12:23,300 --> 00:12:25,373 And it looks like there are 11. 263 00:12:27,220 --> 00:12:29,860 All right. So as a conclusion 264 00:12:29,860 --> 00:12:32,700 to this video sets are not intended 265 00:12:32,700 --> 00:12:35,310 to replace arrays at all. 266 00:12:35,310 --> 00:12:37,960 So whenever you need to store values in order, 267 00:12:37,960 --> 00:12:40,180 and that might contain duplicates, 268 00:12:40,180 --> 00:12:42,220 always just use arrays. 269 00:12:42,220 --> 00:12:43,880 That's also true when you need 270 00:12:43,880 --> 00:12:45,810 to really manipulate data, 271 00:12:45,810 --> 00:12:48,580 because arrays have access to a lot 272 00:12:48,580 --> 00:12:50,360 of great array methods 273 00:12:50,360 --> 00:12:52,890 that we're going to study a little bit later. 274 00:12:52,890 --> 00:12:55,350 Now sets have this very useful property 275 00:12:55,350 --> 00:12:57,200 of being unique. 276 00:12:57,200 --> 00:12:59,690 And it's also very easy to interact 277 00:12:59,690 --> 00:13:01,620 with sets by using all 278 00:13:01,620 --> 00:13:03,910 of their straightforward methods. 279 00:13:03,910 --> 00:13:08,000 However, they are not nearly as important as arrays. 280 00:13:08,000 --> 00:13:10,620 So keep sets in mind when you need to work 281 00:13:10,620 --> 00:13:12,170 with unique values. 282 00:13:12,170 --> 00:13:15,883 But besides that, you can just continue using arrays.