WEBVTT 1 00:00:01.260 --> 00:00:05.730 Okay, so now we know about find and findindex, 2 00:00:05.730 --> 00:00:08.340 but there are actually two additional methods 3 00:00:08.340 --> 00:00:10.980 that were added in ES 2023, 4 00:00:10.980 --> 00:00:13.620 and those are called findlast and findlastindex. 5 00:00:15.300 --> 00:00:19.110 So these are basically counterparts to find and findindex 6 00:00:19.110 --> 00:00:21.150 because as their name says, 7 00:00:21.150 --> 00:00:24.240 they do the exact same thing as these two, 8 00:00:24.240 --> 00:00:28.233 but they start searching from the last to the first element. 9 00:00:29.970 --> 00:00:32.910 Now, let's just, as always, 10 00:00:32.910 --> 00:00:35.130 start by logging our movements here, 11 00:00:35.130 --> 00:00:39.630 so that later we actually see if our results are correct. 12 00:00:39.630 --> 00:00:43.350 And so now, using the findlast method, 13 00:00:43.350 --> 00:00:46.800 I want to determine the last withdrawal, 14 00:00:46.800 --> 00:00:50.370 so lastwithdrawal. 15 00:00:50.370 --> 00:00:54.060 So it's a bit hard to type, but we can do it. 16 00:00:54.060 --> 00:00:57.150 So again, now on movement, 17 00:00:57.150 --> 00:01:01.383 we're going to not call the find method, but findlast. 18 00:01:04.410 --> 00:01:06.060 And so, as we already know, 19 00:01:06.060 --> 00:01:09.360 a withdrawal happens whenever the value of the movement 20 00:01:09.360 --> 00:01:10.650 is less than zero. 21 00:01:10.650 --> 00:01:14.100 So this kind of condition that we're writing here now, 22 00:01:14.100 --> 00:01:18.600 we have written it many times before, so nothing new here. 23 00:01:18.600 --> 00:01:20.100 So less than zero, 24 00:01:20.100 --> 00:01:23.943 and then let's log it to the console as well, 25 00:01:25.410 --> 00:01:27.379 so lastwithdrawal. 26 00:01:27.379 --> 00:01:29.940 And so, as expected, we get -130, 27 00:01:31.800 --> 00:01:35.190 because now the method is starting to look here 28 00:01:35.190 --> 00:01:36.990 from the end of the array. 29 00:01:36.990 --> 00:01:39.420 So it's basically finding the last value 30 00:01:39.420 --> 00:01:42.780 that is less than zero, which is this one right here. 31 00:01:42.780 --> 00:01:46.230 If we were, just like before, using the find method, 32 00:01:46.230 --> 00:01:48.630 then we would get this one right here. 33 00:01:48.630 --> 00:01:52.713 So the first starting to look from the beginning, so -400. 34 00:01:54.960 --> 00:01:57.960 So, that's actually it about this method. 35 00:01:57.960 --> 00:02:01.800 As defined, lastindex is also pretty simple, 36 00:02:01.800 --> 00:02:04.950 so it's basically just like findindex. 37 00:02:04.950 --> 00:02:07.650 So let's do a nice small challenge here, 38 00:02:07.650 --> 00:02:08.820 and actually, if you want, 39 00:02:08.820 --> 00:02:12.510 you can really pause the video and do this as a challenge, 40 00:02:12.510 --> 00:02:15.990 but we can also just do it together here if you like. 41 00:02:15.990 --> 00:02:19.680 So what I want to do is to use this method 42 00:02:19.680 --> 00:02:21.843 to print a string like this. 43 00:02:23.370 --> 00:02:28.370 So your latest large movement was, 44 00:02:30.630 --> 00:02:35.610 and then a number here, X movements ago. 45 00:02:35.610 --> 00:02:38.910 And notice the part of ago here, 46 00:02:38.910 --> 00:02:42.060 which implies, again, that we're counting from the end. 47 00:02:42.060 --> 00:02:44.610 And so basically, these two methods, 48 00:02:44.610 --> 00:02:49.560 so findlast and findlastindex are very, very useful 49 00:02:49.560 --> 00:02:52.080 when we're dealing with sorted data 50 00:02:52.080 --> 00:02:55.890 and are interested in getting the most recent occurrence 51 00:02:55.890 --> 00:03:00.000 of something in this array, or basically in other words, 52 00:03:00.000 --> 00:03:02.880 the latest addition to the array. 53 00:03:02.880 --> 00:03:05.700 And so here, we're also basically assuming 54 00:03:05.700 --> 00:03:08.640 that these movements here happen in order, 55 00:03:08.640 --> 00:03:11.100 so first this one, then this one, this one, 56 00:03:11.100 --> 00:03:12.900 and so on and so forth. 57 00:03:12.900 --> 00:03:15.030 That's why here we said that 58 00:03:15.030 --> 00:03:17.040 this one here was the last withdrawal, 59 00:03:17.040 --> 00:03:19.500 so in this ordered array of movements, 60 00:03:19.500 --> 00:03:21.540 this one here is indeed the last. 61 00:03:21.540 --> 00:03:24.810 And so again, for finding the last occurrence 62 00:03:24.810 --> 00:03:27.210 or the most recent occurrence, 63 00:03:27.210 --> 00:03:30.150 it is useful to start looking from the end, 64 00:03:30.150 --> 00:03:34.830 and so that's when findlast and findlastindex become useful. 65 00:03:34.830 --> 00:03:36.570 And so here in this case, 66 00:03:36.570 --> 00:03:40.620 we're basically gonna look for how many movements ago 67 00:03:40.620 --> 00:03:43.920 the last large movement happened, 68 00:03:43.920 --> 00:03:48.920 and with large, we mean greater than 2000 euros 69 00:03:49.320 --> 00:03:51.990 or dollars or whatever it is here. 70 00:03:51.990 --> 00:03:53.910 All right, so again, if you want, 71 00:03:53.910 --> 00:03:55.620 you can do this as a challenge, 72 00:03:55.620 --> 00:03:57.690 or we can just do it together here. 73 00:03:57.690 --> 00:03:58.983 So let's do that now. 74 00:04:02.670 --> 00:04:06.210 So let's find the index 75 00:04:06.210 --> 00:04:09.930 of the latest large movement here first. 76 00:04:09.930 --> 00:04:11.380 So, latestlargemovementindex, 77 00:04:15.840 --> 00:04:19.590 and again, I like to use these pretty long variable names 78 00:04:19.590 --> 00:04:21.330 just because they're so descriptive. 79 00:04:21.330 --> 00:04:23.940 If someone else reads this code in the future, 80 00:04:23.940 --> 00:04:26.190 they will know exactly what kind of value 81 00:04:26.190 --> 00:04:30.060 is stored in that variable. 82 00:04:30.060 --> 00:04:31.853 So, findlastindex. 83 00:04:36.030 --> 00:04:38.850 And then here again, we get all our movements, 84 00:04:38.850 --> 00:04:41.640 and now here, it doesn't really matter 85 00:04:41.640 --> 00:04:45.150 whether this movement was a withdrawal or a deposit, 86 00:04:45.150 --> 00:04:46.410 it's just a movement. 87 00:04:46.410 --> 00:04:50.190 So we're not interested here in the sign of the number, 88 00:04:50.190 --> 00:04:52.440 so whether it is positive or negative, 89 00:04:52.440 --> 00:04:57.330 so we just take the absolute value of it. 90 00:04:57.330 --> 00:04:58.953 So this we already did before, 91 00:05:00.570 --> 00:05:03.990 so just the value of the movement 92 00:05:03.990 --> 00:05:07.053 needs to be larger than 2000 here. 93 00:05:09.000 --> 00:05:11.463 So let's check if we got this correct. 94 00:05:15.300 --> 00:05:20.073 And so, the result is three, so zero, one, two, three. 95 00:05:20.940 --> 00:05:22.050 Now in this case, 96 00:05:22.050 --> 00:05:24.600 actually it would've been the same result 97 00:05:24.600 --> 00:05:27.540 using findlastindex or findindex 98 00:05:27.540 --> 00:05:29.490 because there is only one value 99 00:05:29.490 --> 00:05:32.100 that satisfies this condition. 100 00:05:32.100 --> 00:05:36.270 So let's actually use greater than 1000 101 00:05:36.270 --> 00:05:37.590 because in this case, 102 00:05:37.590 --> 00:05:40.860 this 1300 here is also a large movement. 103 00:05:40.860 --> 00:05:44.790 And so, then the last index should be this one, 104 00:05:44.790 --> 00:05:47.940 and indeed, now it is number seven. 105 00:05:47.940 --> 00:05:52.200 So zero, one, two, three, four, five, six, seven. 106 00:05:52.200 --> 00:05:55.020 Great, and now let's use this value 107 00:05:55.020 --> 00:05:57.990 to lock this string here to the console. 108 00:05:57.990 --> 00:05:59.673 So let's grab this from here, 109 00:06:01.160 --> 00:06:03.003 and let's leave that there, why not? 110 00:06:03.870 --> 00:06:06.690 Console.log like this, 111 00:06:06.690 --> 00:06:09.873 and let's make a template literal here. 112 00:06:11.880 --> 00:06:15.600 But here, we cannot just plug in this value like this. 113 00:06:15.600 --> 00:06:17.193 So latest. 114 00:06:18.972 --> 00:06:21.422 Well actually, this is not the correct name here, 115 00:06:23.400 --> 00:06:27.843 so latest, it was a typo there. 116 00:06:32.550 --> 00:06:35.160 Right, because the latest large movement 117 00:06:35.160 --> 00:06:37.410 was not zero movements ago, 118 00:06:37.410 --> 00:06:40.290 but really just this one movement ago, 119 00:06:40.290 --> 00:06:42.930 so basically, the last movement here. 120 00:06:42.930 --> 00:06:46.230 And so, we can just subtract this value here 121 00:06:46.230 --> 00:06:48.300 from the total length of the array, 122 00:06:48.300 --> 00:06:51.000 so to get the value that we want here. 123 00:06:51.000 --> 00:06:52.680 So again, this now has nothing to do 124 00:06:52.680 --> 00:06:55.710 with this method here anymore. 125 00:06:55.710 --> 00:06:59.610 This is just us trying to get the value that we want 126 00:06:59.610 --> 00:07:02.373 to solve this challenge that we set for ourself. 127 00:07:03.360 --> 00:07:07.050 So, movements.length 128 00:07:07.050 --> 00:07:09.330 and then minus this, 129 00:07:09.330 --> 00:07:12.630 which gives us was one movement ago. 130 00:07:12.630 --> 00:07:16.200 But let's assume that this here is actually zero movements, 131 00:07:16.200 --> 00:07:19.140 so that if you want to say that it happened just now. 132 00:07:19.140 --> 00:07:22.410 So since the index is zero based 133 00:07:22.410 --> 00:07:25.140 but the length is really eight, 134 00:07:25.140 --> 00:07:26.640 so the length of the array is eight, 135 00:07:26.640 --> 00:07:29.250 but this last element is number seven. 136 00:07:29.250 --> 00:07:32.133 We just need to subtract always just one more here. 137 00:07:33.510 --> 00:07:36.780 And so, it was zero movements ago. 138 00:07:36.780 --> 00:07:38.160 If you were to go back 139 00:07:38.160 --> 00:07:40.980 to the initial thing that we had here, 140 00:07:40.980 --> 00:07:43.020 then it would be four movements ago, 141 00:07:43.020 --> 00:07:46.230 so zero, one, two, three, four. 142 00:07:46.230 --> 00:07:48.240 And maybe it would make a bit more sense, 143 00:07:48.240 --> 00:07:51.180 if this was actually five movements ago, 144 00:07:51.180 --> 00:07:54.840 and this one here was one, as it was initially. 145 00:07:54.840 --> 00:07:57.660 So let's just get rid of this part again, 146 00:07:57.660 --> 00:07:59.250 and this is a bit more natural. 147 00:07:59.250 --> 00:08:00.990 So now, this was five movements ago, 148 00:08:00.990 --> 00:08:04.260 and if it was like this, if this was the large movement, 149 00:08:04.260 --> 00:08:05.940 then it would be one movement ago. 150 00:08:05.940 --> 00:08:06.993 This one right there. 151 00:08:07.830 --> 00:08:11.340 Now, all right, and this is all for this lecture, 152 00:08:11.340 --> 00:08:14.940 and so let's move on to some more array methods. 153 00:08:14.940 --> 00:08:16.650 We're still not done here. 154 00:08:16.650 --> 00:08:17.853 There's a lot to come.