WEBVTT 1 00:00:01.230 --> 00:00:05.013 Let's continue with some simple string methods, 2 00:00:06.780 --> 00:00:08.460 and the first two are gonna be 3 00:00:08.460 --> 00:00:10.953 for changing the case of a string. 4 00:00:14.070 --> 00:00:16.053 So that's airline.toLowerCase, 5 00:00:20.580 --> 00:00:24.450 and this doesn't require any arguments at all. 6 00:00:24.450 --> 00:00:27.210 And then we also have toUpperCase. 7 00:00:27.210 --> 00:00:29.013 And these we use all the time, 8 00:00:30.210 --> 00:00:34.590 as you will see soon in a more real-world example. 9 00:00:34.590 --> 00:00:37.770 And here you see that indeed they transform the string 10 00:00:37.770 --> 00:00:41.370 all to lowercase and to uppercase. 11 00:00:41.370 --> 00:00:44.100 And again, you can, of course, call this directly 12 00:00:44.100 --> 00:00:45.453 also on a string. 13 00:00:46.710 --> 00:00:49.473 So like this, all right. 14 00:00:52.590 --> 00:00:56.430 But now, let's use this on a more practical example 15 00:00:56.430 --> 00:00:59.643 to fix the capitalization in a passenger name. 16 00:01:03.027 --> 00:01:07.233 ... in name, okay. 17 00:01:09.720 --> 00:01:11.220 So let's say that the passenger, 18 00:01:11.220 --> 00:01:14.370 when he checked in, misspelled his name, 19 00:01:14.370 --> 00:01:17.790 and so it looks like this now. 20 00:01:17.790 --> 00:01:19.980 And so this needs to be fixed, 21 00:01:19.980 --> 00:01:23.973 it should look like this, okay. 22 00:01:25.020 --> 00:01:27.600 So in order to fix it, the first step 23 00:01:27.600 --> 00:01:30.543 is usually to put everything into lowercase here. 24 00:01:31.830 --> 00:01:36.830 So const passengerLower is passenger.toLowerCase, like this. 25 00:01:44.790 --> 00:01:49.320 Okay, so basically we already have now this part here, 26 00:01:49.320 --> 00:01:51.930 and now all we need to do is to essentially 27 00:01:51.930 --> 00:01:55.860 take the first letter and then the rest of the string, 28 00:01:55.860 --> 00:01:58.203 and put these two parts back together. 29 00:02:00.210 --> 00:02:05.210 So passengerCorrect will be passengerLowercase, 30 00:02:10.080 --> 00:02:12.720 and here we only need the first letter. 31 00:02:12.720 --> 00:02:14.610 So how do we do that? 32 00:02:14.610 --> 00:02:18.930 We take the first letter by using the index zero. 33 00:02:18.930 --> 00:02:23.930 And so this one, we now convert to uppercase, all right. 34 00:02:24.450 --> 00:02:27.753 And now we simply need to add the rest of the string. 35 00:02:28.770 --> 00:02:32.160 So, again, we take passengerLower, 36 00:02:32.160 --> 00:02:34.050 and then we use the slice 37 00:02:34.050 --> 00:02:35.970 that we learned in the last lecture 38 00:02:35.970 --> 00:02:38.250 and start at position number one, 39 00:02:38.250 --> 00:02:41.700 because, remember, that will then go to index one 40 00:02:41.700 --> 00:02:45.423 and take everything until the end of the string. 41 00:02:47.250 --> 00:02:50.410 And so here we then put back together 42 00:02:51.450 --> 00:02:53.940 just the first part of the string, 43 00:02:53.940 --> 00:02:55.890 converted to uppercase here, 44 00:02:55.890 --> 00:02:58.020 and then the rest of the string 45 00:02:58.020 --> 00:03:00.783 that we already had to lowercase before. 46 00:03:03.510 --> 00:03:08.510 Okay, and indeed now it is corrected. Great. 47 00:03:10.470 --> 00:03:13.590 And of course, we could have done a function with this, 48 00:03:13.590 --> 00:03:16.560 and so maybe if you have the time you can do that. 49 00:03:16.560 --> 00:03:19.800 So just create a function that takes any passenger name 50 00:03:19.800 --> 00:03:22.770 and then returns the correct one, 51 00:03:22.770 --> 00:03:25.650 so with the fixed capitalization. 52 00:03:25.650 --> 00:03:29.640 But, anyway, I will now do another real-life example, 53 00:03:29.640 --> 00:03:34.110 which is to check a user-input email, okay. 54 00:03:34.110 --> 00:03:35.883 So check email. 55 00:03:36.780 --> 00:03:39.330 Now, this will not be really a checking, 56 00:03:39.330 --> 00:03:42.150 it will more be a comparing. 57 00:03:42.150 --> 00:03:44.313 So comparing emails. 58 00:03:46.200 --> 00:03:49.473 So let's say that we have the email of one passenger, 59 00:03:51.330 --> 00:03:55.863 so hello@jonas.io. 60 00:03:57.150 --> 00:03:59.073 But now, as the user logs in, 61 00:04:01.080 --> 00:04:06.080 so let's say loginEmail, accidentally, they do it all wrong, 62 00:04:07.740 --> 00:04:10.950 and they start with a couple of spaces here, 63 00:04:10.950 --> 00:04:15.417 and then the capitalization is all completely off like this. 64 00:04:17.610 --> 00:04:19.770 And then maybe even another space 65 00:04:19.770 --> 00:04:24.770 or even an enter character, which, remember, is \n. 66 00:04:25.140 --> 00:04:28.860 So I think we talked about that in the beginning, okay. 67 00:04:28.860 --> 00:04:31.800 But, still, this email here is actually 68 00:04:31.800 --> 00:04:35.130 still kind of correct and kind of valid. 69 00:04:35.130 --> 00:04:37.410 And so we can now still compare 70 00:04:37.410 --> 00:04:41.490 if these two are kind of the same, okay. 71 00:04:41.490 --> 00:04:45.360 So we can now try to convert this one to this one 72 00:04:45.360 --> 00:04:47.160 and then check if they are the same, 73 00:04:48.060 --> 00:04:50.850 because essentially, again, they are. 74 00:04:50.850 --> 00:04:54.180 They would be different if we had different letters here, 75 00:04:54.180 --> 00:04:56.400 then, of course, they would not be the same, 76 00:04:56.400 --> 00:04:59.580 but here it's just a matter of capitalization. 77 00:04:59.580 --> 00:05:02.760 And for emails, I believe that they are still valid 78 00:05:02.760 --> 00:05:05.040 even with the capitalization off. 79 00:05:05.040 --> 00:05:07.677 And so when we check user input like this, 80 00:05:07.677 --> 00:05:11.433 the first step is usually to convert it to lowercase. 81 00:05:12.960 --> 00:05:17.960 So lowerEmail is loginEmail.toLowerCase, 82 00:05:24.090 --> 00:05:28.050 and then we must also get rid of all the whitespace here. 83 00:05:28.050 --> 00:05:33.010 So these empty spaces and also this enter, basically, here 84 00:05:35.490 --> 00:05:37.680 also count as whitespace. 85 00:05:37.680 --> 00:05:39.963 So there is even a method for that. 86 00:05:41.220 --> 00:05:46.220 So, let's say, trimmedEmail, and so that is lowerEmail.trim. 87 00:05:52.560 --> 00:05:55.410 All right, let's just now log this 88 00:05:55.410 --> 00:05:57.060 through the console, just to see. 89 00:05:58.170 --> 00:06:01.443 And so that looks exactly like that first version. 90 00:06:02.820 --> 00:06:05.910 Now, just look closely at what we did here. 91 00:06:05.910 --> 00:06:09.900 So we called toLowerCase on this loginEmail, 92 00:06:09.900 --> 00:06:11.670 stored it to this variable, 93 00:06:11.670 --> 00:06:15.720 and then on that variable we called the trim method. 94 00:06:15.720 --> 00:06:19.650 But why do we even need this intermediate email? 95 00:06:19.650 --> 00:06:21.663 We could do this all in one step. 96 00:06:23.820 --> 00:06:26.580 So basically, we can replace all of this, 97 00:06:26.580 --> 00:06:30.453 and let's call this normalizedEmail, actually. 98 00:06:32.280 --> 00:06:35.760 And so, again, I will start from loginEmail 99 00:06:35.760 --> 00:06:37.443 and then do it all in one step. 100 00:06:39.577 --> 00:06:40.660 .toLowerCase. 101 00:06:41.940 --> 00:06:44.940 And now this is a bit similar to what we did before 102 00:06:44.940 --> 00:06:47.103 with the map set method. 103 00:06:48.420 --> 00:06:51.123 So this here will return a new string, 104 00:06:52.380 --> 00:06:55.590 and on strings we can call string methods. 105 00:06:55.590 --> 00:06:57.420 And therefore, right here, 106 00:06:57.420 --> 00:07:01.473 we can now immediately call the trim method. 107 00:07:04.770 --> 00:07:09.770 So normalizedEmail, and that should look exactly the same. 108 00:07:11.040 --> 00:07:16.040 And it does, so let's get rid of this. 109 00:07:17.370 --> 00:07:21.453 And these two I will simply leave as a comment here. 110 00:07:23.490 --> 00:07:26.520 And now, just to finish, let's actually also compare them 111 00:07:26.520 --> 00:07:28.533 for the sake of completion. 112 00:07:30.000 --> 00:07:31.860 And once again, you could do this here 113 00:07:31.860 --> 00:07:34.110 in a separate function. 114 00:07:34.110 --> 00:07:37.560 So you could do a function for this behavior 115 00:07:37.560 --> 00:07:39.600 where you pass in two emails, 116 00:07:39.600 --> 00:07:41.370 one which is the correct one 117 00:07:41.370 --> 00:07:43.650 and one which is the one to check, 118 00:07:43.650 --> 00:07:47.463 and then you could return either true or false from that. 119 00:07:48.330 --> 00:07:51.000 So again, that sounds like a good challenge 120 00:07:51.000 --> 00:07:53.103 that you can take if you want. 121 00:07:54.150 --> 00:07:57.930 And by the way, here, since ES2019, 122 00:07:57.930 --> 00:08:00.900 there's also trimStart and trimEnd, 123 00:08:00.900 --> 00:08:04.620 which, as their names say, you can use to trim whitespace 124 00:08:04.620 --> 00:08:08.463 only from the start of the string or only from the end. 125 00:08:09.510 --> 00:08:11.580 Next up, let's learn one of the most 126 00:08:11.580 --> 00:08:13.620 important thing about strings, 127 00:08:13.620 --> 00:08:16.593 which is to replace parts of strings. 128 00:08:19.110 --> 00:08:22.563 So replacing, okay. 129 00:08:23.550 --> 00:08:26.400 And we're gonna stay here again with the airlines. 130 00:08:26.400 --> 00:08:29.433 So let's say we have the price of a flight, 131 00:08:30.900 --> 00:08:35.900 and that price is for Great Britain, so let's say 288,97£. 132 00:08:42.540 --> 00:08:46.680 And you can use any other currency sign that you want here. 133 00:08:46.680 --> 00:08:48.690 What's important is that here in Europe, 134 00:08:48.690 --> 00:08:51.930 we use the comma as a decimal separator, 135 00:08:51.930 --> 00:08:56.930 unlike in the US, where you use the period, so the dot. 136 00:08:57.120 --> 00:08:59.400 And so that's actually what we're gonna do now, 137 00:08:59.400 --> 00:09:03.003 we want to compute the price in the US. 138 00:09:04.770 --> 00:09:07.890 All right, and so for that we will need to replace 139 00:09:07.890 --> 00:09:09.930 the pound with the dollar sign 140 00:09:09.930 --> 00:09:13.263 and the comma with the period. 141 00:09:14.460 --> 00:09:17.470 So that's easy enough, priceGB.replace, 142 00:09:21.150 --> 00:09:23.490 and now here two arguments. 143 00:09:23.490 --> 00:09:26.193 The first one is the one we want to replace, 144 00:09:27.090 --> 00:09:29.610 and let's start here with the pound sign. 145 00:09:29.610 --> 00:09:31.890 And the second argument is the string 146 00:09:31.890 --> 00:09:34.263 that will replace the first one. 147 00:09:38.280 --> 00:09:40.713 So let's take a look, priceUS. 148 00:09:43.410 --> 00:09:45.420 And so that already worked. 149 00:09:45.420 --> 00:09:48.543 And now we need to replace also the comma with the period. 150 00:09:49.530 --> 00:09:52.230 So we could create another variable now, 151 00:09:52.230 --> 00:09:55.020 but instead we will do chaining again, 152 00:09:55.020 --> 00:09:56.670 just like we did before. 153 00:09:56.670 --> 00:10:01.350 And for the same reason, because this returns a string. 154 00:10:01.350 --> 00:10:02.550 And so, on that string 155 00:10:02.550 --> 00:10:07.410 we will immediately call the next replace method. 156 00:10:07.410 --> 00:10:12.093 And now, we are replacing the comma with the dot. 157 00:10:12.960 --> 00:10:16.143 And so, indeed, now we have the price in US. 158 00:10:18.780 --> 00:10:22.530 But, indeed, we can also replace entire words, 159 00:10:22.530 --> 00:10:25.140 not just single characters. 160 00:10:25.140 --> 00:10:26.820 So let's create an announcement 161 00:10:26.820 --> 00:10:30.007 that you would typically hear at the airport, like, 162 00:10:30.007 --> 00:10:35.007 "All passengers come to boarding door 23. Boarding door 23." 163 00:10:43.050 --> 00:10:47.250 However, usually, it is called a gate and not door, 164 00:10:47.250 --> 00:10:48.930 and so, let's replace that 165 00:10:48.930 --> 00:10:51.453 and log the results to the console immediately, 166 00:10:53.190 --> 00:10:56.340 because, just like the other method that we studied, 167 00:10:56.340 --> 00:10:59.370 replace also creates a brand-new string. 168 00:10:59.370 --> 00:11:02.370 It doesn't mutate the original one. 169 00:11:02.370 --> 00:11:03.900 And so here, it's the same, 170 00:11:03.900 --> 00:11:07.593 and so we need to log the actual result to the console. 171 00:11:09.210 --> 00:11:14.210 So, replace door with gate. 172 00:11:15.660 --> 00:11:20.463 Here it's boarding, and now let's check it out here. 173 00:11:21.960 --> 00:11:23.820 So here, boarding gate, 174 00:11:23.820 --> 00:11:27.870 but then here you actually still have boarding door. 175 00:11:27.870 --> 00:11:30.390 And so this replace only replaced 176 00:11:30.390 --> 00:11:34.023 the first occurrence of this search string here. 177 00:11:35.490 --> 00:11:37.560 And actually, that's completely normal, 178 00:11:37.560 --> 00:11:40.770 that's just how the replace method works. 179 00:11:40.770 --> 00:11:43.770 So, again, this method will only replace 180 00:11:43.770 --> 00:11:48.060 the very first occurrence of this search string. 181 00:11:48.060 --> 00:11:49.830 So in this case the door, 182 00:11:49.830 --> 00:11:52.770 but the rest of them will simply stay the same, 183 00:11:52.770 --> 00:11:55.200 so they will not get updated. 184 00:11:55.200 --> 00:12:00.150 But fortunately for us, there's also the replaceAll method, 185 00:12:00.150 --> 00:12:01.830 which, as the name says, 186 00:12:01.830 --> 00:12:05.070 will actually replace all the occurrences 187 00:12:05.070 --> 00:12:06.810 of the search string. 188 00:12:06.810 --> 00:12:10.290 So in this case, it will replace all the doors 189 00:12:10.290 --> 00:12:12.663 with gates, basically. 190 00:12:13.710 --> 00:12:16.740 Now, at the time that I was recording this video 191 00:12:16.740 --> 00:12:20.280 this method wasn't available in JavaScript yet, 192 00:12:20.280 --> 00:12:23.610 and so that's why here we get this error. 193 00:12:23.610 --> 00:12:25.440 But never mind about this, 194 00:12:25.440 --> 00:12:28.020 because now that you're watching this video 195 00:12:28.020 --> 00:12:29.760 this will actually work, 196 00:12:29.760 --> 00:12:31.950 and so you should definitely go ahead 197 00:12:31.950 --> 00:12:34.500 and use this solution right here, 198 00:12:34.500 --> 00:12:36.600 so, the replaceAll method, 199 00:12:36.600 --> 00:12:39.660 whenever you need to replace multiple occurrences 200 00:12:39.660 --> 00:12:44.160 of a certain substring inside the bigger string. 201 00:12:44.160 --> 00:12:48.030 Now, besides this solution, there's also another solution 202 00:12:48.030 --> 00:12:51.600 that was available before we had the replaceAll method, 203 00:12:51.600 --> 00:12:54.480 which involves using a regular expression, 204 00:12:54.480 --> 00:12:57.510 which is what I'm going to show you next. 205 00:12:57.510 --> 00:13:00.990 Now, regular expressions are one of the most complex 206 00:13:00.990 --> 00:13:03.510 and confusing topics of programming, 207 00:13:03.510 --> 00:13:05.190 but for now we are just gonna use 208 00:13:05.190 --> 00:13:09.840 a very simple, regular expression to tell the replace method 209 00:13:09.840 --> 00:13:11.520 that it should actually target 210 00:13:11.520 --> 00:13:16.143 all the occurrences of door here and not just the first one. 211 00:13:17.250 --> 00:13:18.963 So let's again copy this here. 212 00:13:20.070 --> 00:13:22.530 And then, to create a regular expression, 213 00:13:22.530 --> 00:13:25.980 we need to write the string between slashes, 214 00:13:25.980 --> 00:13:27.693 so not between quotes. 215 00:13:29.910 --> 00:13:31.560 So it turned yellow here, again, 216 00:13:31.560 --> 00:13:34.800 which means that it's some kind of string, 217 00:13:34.800 --> 00:13:38.190 but it is now a so-called regular expression. 218 00:13:38.190 --> 00:13:39.960 Then in this case, all we want to do 219 00:13:39.960 --> 00:13:44.960 with this regular expression is to add this g flag here, 220 00:13:45.000 --> 00:13:47.460 and this stands for global. 221 00:13:47.460 --> 00:13:49.530 And that's actually it. 222 00:13:49.530 --> 00:13:52.860 So right now, all the occurrences will be targeted, 223 00:13:52.860 --> 00:13:56.433 and so we replaced gate here and here. 224 00:13:57.420 --> 00:14:01.050 All right, and just as a side note here, 225 00:14:01.050 --> 00:14:03.810 once more, the replace method is, of course, 226 00:14:03.810 --> 00:14:05.880 also case-sensitive. 227 00:14:05.880 --> 00:14:09.153 So just like all of the other string methods are. 228 00:14:10.080 --> 00:14:13.650 Okay, and now as a final topic of this lecture, 229 00:14:13.650 --> 00:14:17.163 there are three simple methods that return booleans. 230 00:14:18.633 --> 00:14:21.720 So, booleans, okay. 231 00:14:21.720 --> 00:14:26.670 And these methods are includes startsWith and endsWith, 232 00:14:26.670 --> 00:14:29.973 so let's create a new plane here, 233 00:14:31.530 --> 00:14:34.023 and that's gonna be the A320neo. 234 00:14:36.390 --> 00:14:39.963 And I'm just missing here the assignment. 235 00:14:41.430 --> 00:14:43.770 And now, we can simply use includes, 236 00:14:43.770 --> 00:14:46.833 just like we can in arrays one more time. 237 00:14:48.990 --> 00:14:52.830 So they have a very similar structure here 238 00:14:52.830 --> 00:14:56.670 in terms of methods that we can use on them. 239 00:14:56.670 --> 00:14:59.040 So, includes, and let's test 240 00:14:59.040 --> 00:15:02.373 if it includes the string A320. 241 00:15:04.320 --> 00:15:06.750 And indeed, it does. 242 00:15:06.750 --> 00:15:10.650 So this airplane here is the Airbus A320neo, 243 00:15:10.650 --> 00:15:13.653 but it still includes just the A320. 244 00:15:15.120 --> 00:15:17.703 Now, let's say if it includes Boeing, 245 00:15:18.930 --> 00:15:21.153 and of course it doesn't. 246 00:15:22.590 --> 00:15:27.590 And now there's another one, which is the startsWith. 247 00:15:30.341 --> 00:15:33.143 And this one is also actually very much used, 248 00:15:34.050 --> 00:15:36.153 I remember using it very recently. 249 00:15:37.230 --> 00:15:41.670 And so in this case here it is false, all right. 250 00:15:41.670 --> 00:15:45.300 But then if we change this here to Airbus, 251 00:15:45.300 --> 00:15:47.493 then it is indeed true. 252 00:15:48.840 --> 00:15:51.570 So these three letters here 253 00:15:51.570 --> 00:15:54.330 are indeed the first three also here, 254 00:15:54.330 --> 00:15:56.853 so it doesn't have to match the entire word. 255 00:15:57.690 --> 00:16:01.050 So just Ai would also be true, 256 00:16:01.050 --> 00:16:06.050 but Aib, let's say, would then be false, 257 00:16:06.300 --> 00:16:08.310 because, of course, the string does not 258 00:16:08.310 --> 00:16:10.740 start with these three letters. 259 00:16:10.740 --> 00:16:13.743 With Airb, then it would again be true. 260 00:16:15.390 --> 00:16:18.333 And of course this A320 is also still true, 261 00:16:19.200 --> 00:16:21.930 as long as it is somewhere in the string. 262 00:16:21.930 --> 00:16:24.273 So now it's somehow here in the middle. 263 00:16:25.680 --> 00:16:29.520 So let's try something very simple here. 264 00:16:29.520 --> 00:16:31.710 So let's say that we want to check 265 00:16:31.710 --> 00:16:36.540 if the current plane is part of the new Airbus family. 266 00:16:36.540 --> 00:16:39.330 And so all we need to do to check that 267 00:16:39.330 --> 00:16:43.323 is to see if the plane name starts with Airbus, 268 00:16:44.460 --> 00:16:46.503 and we can already confirm that it is. 269 00:16:49.140 --> 00:16:54.140 And we also need to check if it ends with neo, 270 00:16:55.350 --> 00:16:57.240 because that means that it's part 271 00:16:57.240 --> 00:17:00.810 of the new Airbus family. 272 00:17:00.810 --> 00:17:02.673 And so we can also use endsWith. 273 00:17:05.760 --> 00:17:08.610 So, as always, these methods here 274 00:17:08.610 --> 00:17:11.520 that return booleans are especially helpful 275 00:17:11.520 --> 00:17:13.473 for conditionals like this, 276 00:17:16.260 --> 00:17:20.793 Part of the NEW Airbus family. 277 00:17:22.410 --> 00:17:24.513 And indeed, this one here is. 278 00:17:25.380 --> 00:17:29.490 But, of course, if it was just a regular A320, 279 00:17:29.490 --> 00:17:32.583 then that would not get logged to the console. 280 00:17:34.050 --> 00:17:36.480 So whenever you need to take some decision 281 00:17:36.480 --> 00:17:39.000 based on the contents of the string, 282 00:17:39.000 --> 00:17:43.170 these three methods are very, very helpful. 283 00:17:43.170 --> 00:17:45.640 And let's now actually practice that a little bit 284 00:17:46.980 --> 00:17:48.153 with some kinds of- 285 00:17:48.990 --> 00:17:51.780 yeah, we can say, a practice exercise. 286 00:17:51.780 --> 00:17:54.330 And so here we want to check if the baggage 287 00:17:54.330 --> 00:17:56.190 of a certain passenger 288 00:17:56.190 --> 00:17:58.833 is basically allowed to be checked in, 289 00:18:00.330 --> 00:18:02.223 so to be allowed on the plane. 290 00:18:03.060 --> 00:18:07.530 So, checkBaggage function, and then here we get the items, 291 00:18:12.300 --> 00:18:14.430 and let me again first call the function 292 00:18:14.430 --> 00:18:15.753 to show you what I mean. 293 00:18:17.970 --> 00:18:21.420 So basically, the passenger here says what they have, 294 00:18:21.420 --> 00:18:26.420 so, "I have a laptop, some food, and a pocket knife." 295 00:18:29.970 --> 00:18:33.093 Then let's call this again and say, 296 00:18:34.918 --> 00:18:38.007 "I have some socks and a camera." 297 00:18:39.180 --> 00:18:42.577 And then, let's call it a third time with the string note, 298 00:18:42.577 --> 00:18:47.577 "Got some snacks and a gun for protection." 299 00:18:49.500 --> 00:18:54.500 Okay, so maybe some passenger would bring a gun to a plane, 300 00:18:55.620 --> 00:18:57.390 but so now let's make sure 301 00:18:57.390 --> 00:19:00.210 they will not get aboard the plane. 302 00:19:00.210 --> 00:19:03.123 And, actually, let's change some things here. 303 00:19:04.200 --> 00:19:05.610 So let's make this uppercase, 304 00:19:05.610 --> 00:19:08.760 let's say this person likes to write 305 00:19:08.760 --> 00:19:10.293 uppercase for some reason. 306 00:19:12.750 --> 00:19:16.200 And so this is important to show you, once again, 307 00:19:16.200 --> 00:19:18.570 that when we receive input from a user 308 00:19:18.570 --> 00:19:20.370 we usually always start 309 00:19:20.370 --> 00:19:23.640 by putting everything into lowercase, 310 00:19:23.640 --> 00:19:25.470 because that makes it a lot easier 311 00:19:25.470 --> 00:19:27.333 to then compare it to something. 312 00:19:29.589 --> 00:19:31.563 (indistinct) say baggage here. 313 00:19:33.030 --> 00:19:36.163 And so, baggage is basically items.toLowerCase. 314 00:19:37.500 --> 00:19:39.153 So this one we use all the time. 315 00:19:40.740 --> 00:19:42.690 And now we can just check if the baggage 316 00:19:42.690 --> 00:19:45.630 includes a knife or a gun, 317 00:19:45.630 --> 00:19:48.663 and in that case the person is not allowed on board. 318 00:19:50.310 --> 00:19:54.213 So, if baggage.includes, 319 00:19:55.650 --> 00:19:59.820 and so here is that method again, which returns a boolean. 320 00:19:59.820 --> 00:20:04.820 So, if it includes knife or if it- 321 00:20:06.480 --> 00:20:11.480 so baggage includes a gun, then we say, 322 00:20:16.957 --> 00:20:21.957 "You are not allowed on board." 323 00:20:24.660 --> 00:20:29.660 else, let's log "Welcome aboard." 324 00:20:33.840 --> 00:20:36.990 And so now let's see here why it is so important 325 00:20:36.990 --> 00:20:39.783 to convert everything first to lowercase. 326 00:20:40.710 --> 00:20:44.490 So in this example here, this first person has knife, 327 00:20:44.490 --> 00:20:46.680 but with an uppercase. 328 00:20:46.680 --> 00:20:50.160 And so if we didn't convert this to lowercase, 329 00:20:50.160 --> 00:20:53.100 then this includes here would be false, 330 00:20:53.100 --> 00:20:55.680 because the lowercase knife is different 331 00:20:55.680 --> 00:20:57.153 than the uppercase knife. 332 00:20:58.530 --> 00:21:02.640 Okay, so let's see the result. 333 00:21:02.640 --> 00:21:05.190 And so indeed, this person has a knife 334 00:21:05.190 --> 00:21:07.230 so they're not allowed. 335 00:21:07.230 --> 00:21:10.680 This person here is fine, and then this one has a gun, 336 00:21:10.680 --> 00:21:13.590 and so, of course, they're also not allowed. 337 00:21:13.590 --> 00:21:17.190 But now, if we took away this here, 338 00:21:17.190 --> 00:21:20.073 well then our code is not really gonna work, 339 00:21:21.540 --> 00:21:25.653 so let's just delete this part for now. 340 00:21:27.030 --> 00:21:30.030 So if we didn't have the toLowerCase, 341 00:21:30.030 --> 00:21:33.510 then the first person would also be "Welcome aboard". 342 00:21:33.510 --> 00:21:37.080 And again, that's because knife here, uppercase, 343 00:21:37.080 --> 00:21:39.000 is different from this knife. 344 00:21:39.000 --> 00:21:42.870 And so then we would have to check for all the variations, 345 00:21:42.870 --> 00:21:47.870 like knife like this, or this knife, or even this. 346 00:21:48.840 --> 00:21:51.510 So every possible variation. 347 00:21:51.510 --> 00:21:54.090 And so that would be highly impractical, 348 00:21:54.090 --> 00:21:56.643 and so we just turn everything to lowercase. 349 00:21:58.530 --> 00:22:01.830 So, again, so that we can then easily compare it 350 00:22:01.830 --> 00:22:05.733 with one standard, which is this and this. 351 00:22:07.410 --> 00:22:09.630 All right, perfect. 352 00:22:09.630 --> 00:22:13.080 So that was another fun lecture, if you ask me, 353 00:22:13.080 --> 00:22:15.840 and I hope you are feeling the same. 354 00:22:15.840 --> 00:22:17.580 Now it's time for a break, 355 00:22:17.580 --> 00:22:20.403 and I'll see you back here in the next video.