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.