Original subtitles

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Let's now return to our code 2

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and learn how logical operators work in JavaScript. 3

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And let's actually use the Boolean variables 4

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from the last lecture. 5

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So the one about having a drivers license 6

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and having good vision. 7

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So, we are gonna create a variable for each of them. 8

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And the first one will be has drivers license 9

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and let's start by setting it to true. 10

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And remember that this one was variable A. 11

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And then let's create has good vision 12

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and also, let's initialize it with true. 13

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So these were the two A and B variables 14

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that we used in the last lecture as an example. 15

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And so it's a good idea to use these here as well. 16

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Okay, but now let's get started with the end 17

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and or operators. 18

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So let's log to the console, of using the end operator 19

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on these two variables. 20

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So has drivers license 21

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and now the end operator in JavaScript is this one. 22

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So it is we can combine two logical values. 23

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So has drivers license and has good vision. 24

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So let's see what the result will be. 25

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So this one is true, right? 26

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And this one is true as well. 27

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So the result of true and true, should be true, right? 28

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So let's see and yes, so that works. 29

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But now, of course, we will change one of them to false. 30

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So remember, the result of true and false will be false, 31

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because it's enough for one variable to be false 32

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for the result of the operation to be false. 33

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And so here, we can now confirm that 34

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and indeed, that is the result. 35

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But now let's see what it would look like 36

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with the OR operator. 37

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So I just copy this and paste it here. 38

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Now, instead of end we use OR and that looks like this. 39

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So again, true or false. 40

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What do you think it will be? 41

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Remember from the last lecture and the result is true. 42

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So it's enough for one of the variables to be true 43

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for the whole operation to become true. 44

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So I hope that's nothing new at this point. 45

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And of course, finally we can also use the NOT operator 46

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to basically invert one of the values. 47

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And the NOT operator in JavaScript is the exclamation mark. 48

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So not has driver's license will become, 49

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so it will change from true to false. 50

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All right, and now since we know how all of this works, 51

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we can use these variables to take a decision. 52

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So let's say that we want to determine 53

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whether Sarah should drive or not. 54

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So let's create a new Boolean variable and use the others 55

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to determine that. 56

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So let's say should drive 57

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and our model is that Sarah should drive, 58

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if she has a driver's license 59

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and at the same time has good vision, okay? 60

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And so as I mentioned in the last lecture, 61

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we can now use these Boolean variables, 62

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and this Boolean logic to model complex situations. 63

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And this one is actually pretty simple, 64

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but we will take it up a notch by the end of this lecture. 65

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So remember, model is that she has a driver's license, 66

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and that she has good vision. 67

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Okay, and now we can use this variable 68

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to finally take the decision. 69

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So let's then use this Boolean variable here and say, 70

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if she should drive, then lock to the console. 71

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Sarah is able to drive 72

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and if not, 73

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just log someone else 74

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should derive. 75

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Now, okay, and actually we can put the condition right here 76

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in the IF condition. 77

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So this was just to show you a little bit 78

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the thought process. 79

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But as I mentioned earlier, 80

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we usually create the condition right here 81

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in the IF statement. 82

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So give it a safe and now let's run it and the result is, 83

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someone else should drive. 84

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So that is because has good vision is false, 85

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and so our condition of has driver's license 86

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and has good vision is not true. 87

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Because it's only true in case that both of them are true, 88

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as you already know by now. 89

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So this one is false right now. 90

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And so therefore the else block will be executed. 91

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But of course, we can change it once more. 92

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And so right now, both of them are true. 93

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So has driver's license true and has good vision true. 94

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So true and true, is true and so Sarah is able to drive. 95

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Let's check that and indeed, great. 96

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And but this one working now perfectly, 97

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let's take it to the next level 98

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and add another Boolean variable here. 99

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So, let's now also add is tired. 100

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And let's set it to true as well. 101

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So we can say that this is our variable C. 102

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So to use more than two variables with, for example, 103

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the end operator, let's just go ahead and copy this one. 104

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So if you want to say has driver's license 105

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or has good vision or is tired. 106

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All you have to do is to add another OR operator here, 107

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just like you would add another plus 108

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or another minus operator. 109

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And the result of this should of course, be true, 110

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because while all of them are true. 111

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And indeed, it is. 112

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And if we set them all to end, 113

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then it is also true, because all of them are true. 114

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And if we set this one to false, 115

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then as you can guess the result will be false. 116

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And that is because as I explained in the last lecture, 117

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it's enough for one of the operands to be false 118

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to make the whole end operation false as well. 119

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Okay, but let it set back to true. 120

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And now, we can use this to improve our decision making, 121

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whether Sarah should drive or not. 122

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So with this third variable now, 123

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we want Sarah to be able to drive 124

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if she has a driver's license, if she has good vision 125

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and if she is not tired, right? 126

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So let's now translate that into a condition. 127

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And I will just copy this one 128

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and then comment all of it out using Command 129

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or Control/ just like many times before 130

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and now we will improve this one. 131

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So this one, of course, is the same 132

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that she needs to have a driver's license and good vision. 133

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But now additionally, we want her to be not tired. 134

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So right now she is tired, it's true 135

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and that's, of course, not good for driving. 136

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So we want the opposite of being tired. 137

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And so therefore, we need to invert it. 138

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So do you remember how that works? 139

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All we need to do is to use the NOT operator. 140

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So not is tired, all right? 141

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So let's read this again, 142

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Sarah is able to drive if she has a driver's license. 143

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So if this one is true, if she has good vision, 144

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so if this one is true and if she is not tired, 145

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so if all of this is true here. 146

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So only in this condition, Sarah is able to drive. 147

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Now how is this part here true? 148

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Well, it's true, when is tired is false, right? 149

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So what do you think will happen 150

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in this situation right now? 151

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Well, let's test and then analyze. 152

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So we get the result, someone else should drive. 153

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So why is that? 154

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Well, this one is true, 155

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this one is true as we see up here, 156

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and then is tired is also true. 157

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However, not is tired is false. 158

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So this part here is false. 159

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And so true and true and false is of course, false. 160

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And so therefore, we get the else block, 161

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someone else should drive. 162

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Now to fix this, 163

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we need to change is tired to false, all right? 164

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And so right now is tired is false 165

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and therefore not is tired will become true. 166

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And then we have true and true and true 167

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and then in this situation, Sarah will be able to drive. 168

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Yes, indeed, it works now. 169

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So as you see, with these three Boolean operators, 170

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we can model all kinds of companies decisions like this one. 171

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Now, I know that this was probably a bit confusing, 172

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but please don't worry too much, 173

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because it's all very confusing for everyone 174

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when they first learn how to program, okay? 175

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Just take some time after this video 176

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and analyze again exactly what happens here. 177

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Maybe also together with the last video 178

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to really make sure that you understand 179

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what is going on here. 180

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But of course, the best way to retain any knowledge 181

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is by practicing and reinforcing it. 182

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And so let's do that now in the next coding challenge.