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These are the user uploaded subtitles that are being translated: 1 1 00:00:01,270 --> 00:00:03,430 Let's now return to our code 2 2 00:00:03,430 --> 00:00:07,253 and learn how logical operators work in JavaScript. 3 3 00:00:09,270 --> 00:00:11,690 And let's actually use the Boolean variables 4 4 00:00:11,690 --> 00:00:13,310 from the last lecture. 5 5 00:00:13,310 --> 00:00:16,520 So the one about having a drivers license 6 6 00:00:16,520 --> 00:00:18,053 and having good vision. 7 7 00:00:20,460 --> 00:00:24,460 So, we are gonna create a variable for each of them. 8 8 00:00:24,460 --> 00:00:28,957 And the first one will be has drivers license 9 9 00:00:30,450 --> 00:00:33,440 and let's start by setting it to true. 10 10 00:00:33,440 --> 00:00:35,970 And remember that this one was variable A. 11 11 00:00:37,576 --> 00:00:41,283 And then let's create has good vision 12 12 00:00:44,190 --> 00:00:46,813 and also, let's initialize it with true. 13 13 00:00:48,250 --> 00:00:51,290 So these were the two A and B variables 14 14 00:00:51,290 --> 00:00:54,450 that we used in the last lecture as an example. 15 15 00:00:54,450 --> 00:00:57,263 And so it's a good idea to use these here as well. 16 16 00:00:58,650 --> 00:01:00,981 Okay, but now let's get started with the end 17 17 00:01:00,981 --> 00:01:03,530 and or operators. 18 18 00:01:03,530 --> 00:01:07,910 So let's log to the console, of using the end operator 19 19 00:01:07,910 --> 00:01:09,910 on these two variables. 20 20 00:01:09,910 --> 00:01:12,460 So has drivers license 21 21 00:01:12,460 --> 00:01:16,990 and now the end operator in JavaScript is this one. 22 22 00:01:16,990 --> 00:01:20,160 So it is we can combine two logical values. 23 23 00:01:20,160 --> 00:01:25,160 So has drivers license and has good vision. 24 24 00:01:26,570 --> 00:01:29,490 So let's see what the result will be. 25 25 00:01:29,490 --> 00:01:32,160 So this one is true, right? 26 26 00:01:32,160 --> 00:01:34,220 And this one is true as well. 27 27 00:01:34,220 --> 00:01:39,220 So the result of true and true, should be true, right? 28 28 00:01:41,200 --> 00:01:46,200 So let's see and yes, so that works. 29 29 00:01:47,010 --> 00:01:50,223 But now, of course, we will change one of them to false. 30 30 00:01:51,410 --> 00:01:56,410 So remember, the result of true and false will be false, 31 31 00:01:56,810 --> 00:01:59,870 because it's enough for one variable to be false 32 32 00:01:59,870 --> 00:02:03,100 for the result of the operation to be false. 33 33 00:02:03,100 --> 00:02:05,360 And so here, we can now confirm that 34 34 00:02:05,360 --> 00:02:07,990 and indeed, that is the result. 35 35 00:02:07,990 --> 00:02:10,450 But now let's see what it would look like 36 36 00:02:10,450 --> 00:02:12,670 with the OR operator. 37 37 00:02:12,670 --> 00:02:16,053 So I just copy this and paste it here. 38 38 00:02:17,070 --> 00:02:21,900 Now, instead of end we use OR and that looks like this. 39 39 00:02:21,900 --> 00:02:25,970 So again, true or false. 40 40 00:02:25,970 --> 00:02:27,620 What do you think it will be? 41 41 00:02:27,620 --> 00:02:32,400 Remember from the last lecture and the result is true. 42 42 00:02:32,400 --> 00:02:35,750 So it's enough for one of the variables to be true 43 43 00:02:35,750 --> 00:02:38,660 for the whole operation to become true. 44 44 00:02:38,660 --> 00:02:42,250 So I hope that's nothing new at this point. 45 45 00:02:42,250 --> 00:02:47,250 And of course, finally we can also use the NOT operator 46 46 00:02:47,490 --> 00:02:50,410 to basically invert one of the values. 47 47 00:02:50,410 --> 00:02:55,090 And the NOT operator in JavaScript is the exclamation mark. 48 48 00:02:55,090 --> 00:02:59,293 So not has driver's license will become, 49 49 00:03:00,670 --> 00:03:04,153 so it will change from true to false. 50 50 00:03:05,210 --> 00:03:09,280 All right, and now since we know how all of this works, 51 51 00:03:09,280 --> 00:03:12,490 we can use these variables to take a decision. 52 52 00:03:12,490 --> 00:03:14,660 So let's say that we want to determine 53 53 00:03:14,660 --> 00:03:17,370 whether Sarah should drive or not. 54 54 00:03:17,370 --> 00:03:20,960 So let's create a new Boolean variable and use the others 55 55 00:03:20,960 --> 00:03:22,183 to determine that. 56 56 00:03:24,620 --> 00:03:29,390 So let's say should drive 57 57 00:03:29,390 --> 00:03:32,070 and our model is that Sarah should drive, 58 58 00:03:32,070 --> 00:03:34,180 if she has a driver's license 59 59 00:03:34,180 --> 00:03:38,040 and at the same time has good vision, okay? 60 60 00:03:38,040 --> 00:03:40,570 And so as I mentioned in the last lecture, 61 61 00:03:40,570 --> 00:03:42,880 we can now use these Boolean variables, 62 62 00:03:42,880 --> 00:03:46,670 and this Boolean logic to model complex situations. 63 63 00:03:46,670 --> 00:03:49,140 And this one is actually pretty simple, 64 64 00:03:49,140 --> 00:03:52,750 but we will take it up a notch by the end of this lecture. 65 65 00:03:52,750 --> 00:03:57,430 So remember, model is that she has a driver's license, 66 66 00:03:57,430 --> 00:04:00,483 and that she has good vision. 67 67 00:04:01,540 --> 00:04:04,700 Okay, and now we can use this variable 68 68 00:04:04,700 --> 00:04:06,903 to finally take the decision. 69 69 00:04:08,010 --> 00:04:12,470 So let's then use this Boolean variable here and say, 70 70 00:04:12,470 --> 00:04:17,470 if she should drive, then lock to the console. 71 71 00:04:19,300 --> 00:04:22,750 Sarah is able to drive 72 72 00:04:24,130 --> 00:04:25,023 and if not, 73 73 00:04:26,460 --> 00:04:30,150 just log someone else 74 74 00:04:32,790 --> 00:04:34,123 should derive. 75 75 00:04:36,530 --> 00:04:40,510 Now, okay, and actually we can put the condition right here 76 76 00:04:40,510 --> 00:04:42,150 in the IF condition. 77 77 00:04:42,150 --> 00:04:44,020 So this was just to show you a little bit 78 78 00:04:44,020 --> 00:04:45,920 the thought process. 79 79 00:04:45,920 --> 00:04:47,300 But as I mentioned earlier, 80 80 00:04:47,300 --> 00:04:50,290 we usually create the condition right here 81 81 00:04:50,290 --> 00:04:52,980 in the IF statement. 82 82 00:04:52,980 --> 00:04:57,980 So give it a safe and now let's run it and the result is, 83 83 00:04:58,620 --> 00:05:01,010 someone else should drive. 84 84 00:05:01,010 --> 00:05:05,880 So that is because has good vision is false, 85 85 00:05:05,880 --> 00:05:08,720 and so our condition of has driver's license 86 86 00:05:08,720 --> 00:05:11,300 and has good vision is not true. 87 87 00:05:11,300 --> 00:05:15,140 Because it's only true in case that both of them are true, 88 88 00:05:15,140 --> 00:05:17,870 as you already know by now. 89 89 00:05:17,870 --> 00:05:20,140 So this one is false right now. 90 90 00:05:20,140 --> 00:05:23,770 And so therefore the else block will be executed. 91 91 00:05:23,770 --> 00:05:26,363 But of course, we can change it once more. 92 92 00:05:27,550 --> 00:05:30,570 And so right now, both of them are true. 93 93 00:05:30,570 --> 00:05:35,310 So has driver's license true and has good vision true. 94 94 00:05:35,310 --> 00:05:40,263 So true and true, is true and so Sarah is able to drive. 95 95 00:05:41,530 --> 00:05:45,970 Let's check that and indeed, great. 96 96 00:05:45,970 --> 00:05:48,510 And but this one working now perfectly, 97 97 00:05:48,510 --> 00:05:50,610 let's take it to the next level 98 98 00:05:50,610 --> 00:05:53,173 and add another Boolean variable here. 99 99 00:05:54,140 --> 00:05:59,133 So, let's now also add is tired. 100 100 00:06:01,370 --> 00:06:03,693 And let's set it to true as well. 101 101 00:06:04,580 --> 00:06:07,363 So we can say that this is our variable C. 102 102 00:06:08,340 --> 00:06:13,130 So to use more than two variables with, for example, 103 103 00:06:13,130 --> 00:06:16,763 the end operator, let's just go ahead and copy this one. 104 104 00:06:17,890 --> 00:06:20,470 So if you want to say has driver's license 105 105 00:06:20,470 --> 00:06:23,600 or has good vision or is tired. 106 106 00:06:23,600 --> 00:06:27,730 All you have to do is to add another OR operator here, 107 107 00:06:27,730 --> 00:06:29,730 just like you would add another plus 108 108 00:06:29,730 --> 00:06:31,563 or another minus operator. 109 109 00:06:33,270 --> 00:06:36,760 And the result of this should of course, be true, 110 110 00:06:36,760 --> 00:06:39,143 because while all of them are true. 111 111 00:06:40,810 --> 00:06:42,323 And indeed, it is. 112 112 00:06:43,170 --> 00:06:45,373 And if we set them all to end, 113 113 00:06:48,220 --> 00:06:53,037 then it is also true, because all of them are true. 114 114 00:06:53,037 --> 00:06:55,430 And if we set this one to false, 115 115 00:06:55,430 --> 00:07:00,320 then as you can guess the result will be false. 116 116 00:07:00,320 --> 00:07:03,100 And that is because as I explained in the last lecture, 117 117 00:07:03,100 --> 00:07:06,230 it's enough for one of the operands to be false 118 118 00:07:06,230 --> 00:07:09,673 to make the whole end operation false as well. 119 119 00:07:12,420 --> 00:07:16,170 Okay, but let it set back to true. 120 120 00:07:16,170 --> 00:07:19,990 And now, we can use this to improve our decision making, 121 121 00:07:19,990 --> 00:07:23,670 whether Sarah should drive or not. 122 122 00:07:23,670 --> 00:07:25,900 So with this third variable now, 123 123 00:07:25,900 --> 00:07:27,910 we want Sarah to be able to drive 124 124 00:07:27,910 --> 00:07:31,970 if she has a driver's license, if she has good vision 125 125 00:07:31,970 --> 00:07:35,460 and if she is not tired, right? 126 126 00:07:35,460 --> 00:07:39,010 So let's now translate that into a condition. 127 127 00:07:39,010 --> 00:07:40,770 And I will just copy this one 128 128 00:07:40,770 --> 00:07:43,820 and then comment all of it out using Command 129 129 00:07:43,820 --> 00:07:47,460 or Control/ just like many times before 130 130 00:07:48,650 --> 00:07:52,030 and now we will improve this one. 131 131 00:07:52,030 --> 00:07:54,500 So this one, of course, is the same 132 132 00:07:54,500 --> 00:07:58,180 that she needs to have a driver's license and good vision. 133 133 00:07:58,180 --> 00:08:02,310 But now additionally, we want her to be not tired. 134 134 00:08:02,310 --> 00:08:05,160 So right now she is tired, it's true 135 135 00:08:05,160 --> 00:08:08,460 and that's, of course, not good for driving. 136 136 00:08:08,460 --> 00:08:11,550 So we want the opposite of being tired. 137 137 00:08:11,550 --> 00:08:15,380 And so therefore, we need to invert it. 138 138 00:08:15,380 --> 00:08:17,080 So do you remember how that works? 139 139 00:08:18,360 --> 00:08:21,760 All we need to do is to use the NOT operator. 140 140 00:08:21,760 --> 00:08:26,520 So not is tired, all right? 141 141 00:08:26,520 --> 00:08:28,930 So let's read this again, 142 142 00:08:28,930 --> 00:08:32,770 Sarah is able to drive if she has a driver's license. 143 143 00:08:32,770 --> 00:08:36,290 So if this one is true, if she has good vision, 144 144 00:08:36,290 --> 00:08:40,120 so if this one is true and if she is not tired, 145 145 00:08:40,120 --> 00:08:42,313 so if all of this is true here. 146 146 00:08:43,420 --> 00:08:46,810 So only in this condition, Sarah is able to drive. 147 147 00:08:46,810 --> 00:08:50,010 Now how is this part here true? 148 148 00:08:50,010 --> 00:08:54,890 Well, it's true, when is tired is false, right? 149 149 00:08:54,890 --> 00:08:56,310 So what do you think will happen 150 150 00:08:56,310 --> 00:08:58,960 in this situation right now? 151 151 00:08:58,960 --> 00:09:01,353 Well, let's test and then analyze. 152 152 00:09:02,350 --> 00:09:05,790 So we get the result, someone else should drive. 153 153 00:09:05,790 --> 00:09:07,590 So why is that? 154 154 00:09:07,590 --> 00:09:09,030 Well, this one is true, 155 155 00:09:09,030 --> 00:09:11,750 this one is true as we see up here, 156 156 00:09:11,750 --> 00:09:14,880 and then is tired is also true. 157 157 00:09:14,880 --> 00:09:18,500 However, not is tired is false. 158 158 00:09:18,500 --> 00:09:20,450 So this part here is false. 159 159 00:09:20,450 --> 00:09:25,000 And so true and true and false is of course, false. 160 160 00:09:25,000 --> 00:09:27,870 And so therefore, we get the else block, 161 161 00:09:27,870 --> 00:09:29,860 someone else should drive. 162 162 00:09:29,860 --> 00:09:30,893 Now to fix this, 163 163 00:09:31,780 --> 00:09:36,780 we need to change is tired to false, all right? 164 164 00:09:37,330 --> 00:09:40,750 And so right now is tired is false 165 165 00:09:40,750 --> 00:09:43,850 and therefore not is tired will become true. 166 166 00:09:43,850 --> 00:09:47,090 And then we have true and true and true 167 167 00:09:47,090 --> 00:09:50,743 and then in this situation, Sarah will be able to drive. 168 168 00:09:51,940 --> 00:09:54,870 Yes, indeed, it works now. 169 169 00:09:54,870 --> 00:09:58,340 So as you see, with these three Boolean operators, 170 170 00:09:58,340 --> 00:10:02,410 we can model all kinds of companies decisions like this one. 171 171 00:10:02,410 --> 00:10:06,090 Now, I know that this was probably a bit confusing, 172 172 00:10:06,090 --> 00:10:07,890 but please don't worry too much, 173 173 00:10:07,890 --> 00:10:10,970 because it's all very confusing for everyone 174 174 00:10:10,970 --> 00:10:14,350 when they first learn how to program, okay? 175 175 00:10:14,350 --> 00:10:16,710 Just take some time after this video 176 176 00:10:16,710 --> 00:10:19,800 and analyze again exactly what happens here. 177 177 00:10:19,800 --> 00:10:22,190 Maybe also together with the last video 178 178 00:10:22,190 --> 00:10:23,970 to really make sure that you understand 179 179 00:10:23,970 --> 00:10:25,890 what is going on here. 180 180 00:10:25,890 --> 00:10:28,860 But of course, the best way to retain any knowledge 181 181 00:10:28,860 --> 00:10:31,840 is by practicing and reinforcing it. 182 182 00:10:31,840 --> 00:10:35,363 And so let's do that now in the next coding challenge. 15854