WEBVTT 1 00:00:01.150 --> 00:00:03.770 Let's now learn about the new operator 2 00:00:03.770 --> 00:00:07.763 with the funny name of nullish coalescing operator. 3 00:00:09.120 --> 00:00:11.810 So in the last video, we used the OR operator 4 00:00:11.810 --> 00:00:13.850 to set a default value 5 00:00:13.850 --> 00:00:18.320 in case that the first value was a falsy value. 6 00:00:18.320 --> 00:00:20.833 So let me bring back that code here, actually. 7 00:00:23.450 --> 00:00:24.593 So this one, 8 00:00:25.890 --> 00:00:30.403 but we're only interested in the OR operator here. 9 00:00:33.620 --> 00:00:36.270 So let's call this one simply guests. 10 00:00:36.270 --> 00:00:39.390 And so let's again remember what happens here, 11 00:00:39.390 --> 00:00:42.310 which is when we set numGuests to zero, 12 00:00:42.310 --> 00:00:46.130 then JavaScript will still take this default value here 13 00:00:46.130 --> 00:00:50.810 and assign it to guests because zero is a falsy value now, 14 00:00:50.810 --> 00:00:54.340 and so therefore, we go to the second operand. 15 00:00:54.340 --> 00:00:56.290 However, fortunately for us, 16 00:00:56.290 --> 00:00:58.950 there is a very good solution to this, 17 00:00:58.950 --> 00:01:01.820 and that's the new operator with the very weird name 18 00:01:01.820 --> 00:01:04.460 of nullish coalescing operator. 19 00:01:04.460 --> 00:01:07.840 It's an operator that was introduced in ES2020, 20 00:01:07.840 --> 00:01:10.290 and it works like this. 21 00:01:10.290 --> 00:01:13.973 So guests, let's call this one Correct now. 22 00:01:15.210 --> 00:01:20.020 And so it works almost the same way as the OR operator, 23 00:01:20.020 --> 00:01:25.020 really almost the same, but it will fix or error here. 24 00:01:25.080 --> 00:01:27.260 So let's see that it does, 25 00:01:27.260 --> 00:01:29.310 and then I'll explain to you why that is. 26 00:01:30.190 --> 00:01:33.160 All right, and now indeed, we get zero. 27 00:01:33.160 --> 00:01:36.360 So we get the real value that is actually here. 28 00:01:36.360 --> 00:01:39.830 And now if we take it off, only then we get 10, 29 00:01:39.830 --> 00:01:43.130 which is the default value that we want. 30 00:01:43.130 --> 00:01:45.230 So why does this work? 31 00:01:45.230 --> 00:01:48.630 Well, it is because the nullish coalescing operator 32 00:01:48.630 --> 00:01:51.450 works with the idea or with the concept 33 00:01:51.450 --> 00:01:54.823 of nullish values instead of falsy values. 34 00:01:57.700 --> 00:02:00.100 And nullish values are null 35 00:02:01.700 --> 00:02:04.660 and undefined. 36 00:02:04.660 --> 00:02:05.580 That's it. 37 00:02:05.580 --> 00:02:09.690 It does not include a zero 38 00:02:09.690 --> 00:02:10.983 or the empty string. 39 00:02:12.080 --> 00:02:15.150 So basically, for the nullish coalescing operator, 40 00:02:15.150 --> 00:02:19.610 it is as if the zero and the empty string 41 00:02:19.610 --> 00:02:21.580 were not falsy values 42 00:02:21.580 --> 00:02:24.580 and were instead truthy values as well. 43 00:02:24.580 --> 00:02:27.290 But again, this operator does work 44 00:02:27.290 --> 00:02:30.260 with the principle of nullish values. 45 00:02:30.260 --> 00:02:32.040 And so all the nullish values 46 00:02:32.040 --> 00:02:34.313 will short circuit the evaluation here. 47 00:02:35.660 --> 00:02:39.260 Okay, so only if this was null or undefined, 48 00:02:39.260 --> 00:02:41.880 only then the second operand here 49 00:02:41.880 --> 00:02:44.640 would be executed and returned. 50 00:02:44.640 --> 00:02:46.690 And so right now, that's the case 51 00:02:46.690 --> 00:02:49.210 as number of guests does not exist, 52 00:02:49.210 --> 00:02:51.300 so we commented it out here. 53 00:02:51.300 --> 00:02:52.950 And so now it is undefined, 54 00:02:52.950 --> 00:02:56.623 and so only then the evaluation continues. 55 00:02:57.630 --> 00:03:01.630 But again, as we put it back, it now is zero, 56 00:03:01.630 --> 00:03:04.410 and zero is not a nullish value. 57 00:03:04.410 --> 00:03:07.900 And therefore, the evaluation here is short circuited, 58 00:03:07.900 --> 00:03:12.313 and immediately, this first non-nullish value is returned. 59 00:03:13.840 --> 00:03:16.240 All right, and that's actually all for now 60 00:03:16.240 --> 00:03:19.040 about this nullish coalescing operator. 61 00:03:19.040 --> 00:03:22.210 It's a really great and really useful operator, 62 00:03:22.210 --> 00:03:26.050 even though right now, it might not seem that useful, 63 00:03:26.050 --> 00:03:27.990 but as we go through the project, 64 00:03:27.990 --> 00:03:29.633 you will see that it really is.