Original subtitles

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And here goes your next coding challenge. 2

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This time number three, 3

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for you to review all the material about objects. 4

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And I hope that you're really doing 5

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all these coding challenges. 6

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Because as I mentioned earlier, 7

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they are really, really important for your progress. 8

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And I designed them all very carefully 9

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to exactly match the progress of the course 10

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and place them in strategic points of the curriculum. 11

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So I cannot stress enough how important it is 12

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that you do these challenges even if it's a bit difficult 13

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but that's why they are called challenges. 14

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They are really to challenge you and to make a thing 15

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and if necessary spent half an hour or one hour 16

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even to really try to figure out how the code works 17

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without coding on your own, 18

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it's impossible to learn programming, believe me. 19

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But anyway, let's now get to the challenge. 20

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And in this one, we're going back to Mark and John comparing 21

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their body mass indexes. 22

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And this time we're gonna use objects 23

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to implement these calculations. 24

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So here we have the formula again to calculate the BMI. 25

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And so your tasks are, first for each of them, 26

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so for Mark and John create an object with properties 27

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for their full name, their mass and their height. 28

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So their full names are actually Mark Miller and John Smith. 29

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Then create a method called calcBMI on each object 30

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which will then calculate the BMI based on the data 31

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that is on the object. 32

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So create the both method and add the exact same method 33

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to both objects. 34

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So write this method first in one of the objects 35

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and then copy the exact same method 36

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without changing it to the other object. 37

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And this method should store the BMI value 38

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to a property and it should also return it from the method. 39

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So a little bit like the cogH method 40

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that we did in the previous lecture 41

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then lock to the console who of the two has to hire a BMI 42

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and this string should look like this. 43

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So it should include the full name 44

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and actually here it's not the full name 45

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but do include the full name that's why we have it. 46

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So John Smith BMI is higher than Mark Miller's. 47

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So not killers, but Mark Millers 48

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and then also include the actual BMI value here. 49

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And here is the test data 50

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and I believe it's the same data as before. 51

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So good luck with this challenge. 52

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And again, it might be challenging 53

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but please give it a try anyway, okay. 54

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So I see you here in a minute 55

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or maybe in half an hour, who knows? 56

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It doesn't matter how long you take. 57

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Now, okay, so let's get to work. 58

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So number one is creating an object for each of them. 59

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So object Mark. 60

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So full name property, Mark Miller, 61

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then the mass which is 78 kilograms 62

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and then the height which is 1.69 meters. 63

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So that's it for now. 64

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And now I'm just gonna copy this, 65

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as always, I'm a bit lazy 66

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and that's just how programmers are, I guess. 67

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So John Smith and he is 92 kilos 68

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and 1.95 meters tall. 69

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Okay, so that is point number one. 70

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And now we will create the cog BMI method. 71

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And then a function without any parameters 72

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because we will take the data directly from the object 73

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just like we did it with the cog H method previously. 74

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And remember that it says here that we should store 75

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the BMI value to a property and also return it 76

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from the method. 77

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So this means that we will do this .BMI 78

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and then do the calculation here. 79

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And remember, from the formula to BMI is calculated 80

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by this .mass divided by this .height squared. 81

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So exponentiation operator with two 82

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and then also return it. 83

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So at this .BMI 84

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and just to see if this actually works, 85

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let's actually call this method. 86

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So mark.calc.BMI 87

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and now I will quickly lock to the console, 88

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the property that we just created. 89

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So I could have locked this to the console directly 90

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but I want to do it this way now. 91

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And it doesn't really matter. 92

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So with this, remember we created a property called BMI. 93

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And so that is now of course accessible here. 94

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So mark.BMI because remember that here in this method, 95

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this now points to Mark because that is the object 96

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that is calling the method 97

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and therefore this .BMI will be on Mark. 98

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So mark.BMI equals mark.mass divided by mark.height. 99

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And so that's how we get this data into this method. 100

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All right, so that's essentially what we learned 101

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in the last lecture. 102

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And so here I'm doing the same. 103

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I'm first calculating this value 104

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and then I'm doing mark.BMI 105

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which was added here in this method call. 106

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Of course without this method call, 107

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mark.BMI would not be available 108

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because this method here it doesn't call itself. 109

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We need to explicitly call it. 110

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Now, console are missing the .log. 111

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How can that still happen after all these years? 112

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Okay, so here we get the BMI of 27 which seems about right. 113

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And now as I said, we will simply go ahead 114

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and copy this method exactly the same to this John object 115

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and it will work just the same, believe me. 116

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So let me show that to you. 117

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So now we call John.calcBMI. 118

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And so now the object calling calcBMI is John. 119

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And so now in this method here, 120

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this will point to the John object. 121

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And so this time John.BMI will be calculated 122

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using John's data of mass and height. 123

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Okay, are you still following that? 124

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As always, you can pause the video, 125

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analyze the code on your own 126

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or you can always rewind to hear the explanation again. 127

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I actually like to do that myself 128

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when I watch other online video courses. 129

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So I think that's a good tip maybe. 130

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Anyway, so we just calculated the BMI of John here as well 131

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and so now I'm logging both to the console. 132

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And so yeah, this one also looks correct. 133

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And so this means that simply copying this method 134

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from one place to the other actually makes it work 135

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and adapt to the data of each objects. 136

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Now having the exact same code in both of these objects, 137

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kind of violates the don't repeat yourself principle, right. 138

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And actually there is a way in which we can avoid this. 139

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And of course we will learn how 140

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at a later point in the course 141

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using something called object oriented programming. 142

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But for now we are still learning the basics 143

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and just want to make things work. 144

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And of course have some fun along the way. 145

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So this was the hardest part I believe 146

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at least now all we have to do is to write this string here. 147

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Let me actually copy the examples 148

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so we have it as a reference down here. 149

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Otherwise I'm gonna get a bit lost. 150

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So if Mark.BMI is larger than John.BMI, then console.log. 151

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So let's get the full name now from the object. 152

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So mark.fullName BMI and now we also need it here 153

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in these parenthesis. 154

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So let's put it there, Mark.BMI is higher than 155

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and I'll let me just copy it here. 156

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So and again, I'm using command D 157

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to select the next occurrence 158

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and then let's just replace it with John. 159

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So Mark's BMI is higher than John's BMI. 160

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And now let's grab this again. 161

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Else if John BMI is larger than Mark.BMI 162

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then essentially say the opposite. 163

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So here it's gonna be John and again command D 164

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and here it's gonna be Mark, okay. 165

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So 27 is higher than 24 and that 27 belongs to Mark. 166

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And so this seems to be about right 167

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but it's not completely right. 168

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So of course here it should be lowercase. 169

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So BMI and now I cannot use the command D 170

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because then it will select this one as well. 171

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So I'm double clicking on this one 172

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and I hope that you're finding 173

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these VS code tips useful as well. 174

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So I'm clicking or actually I'm double clicking on this one, 175

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Then I hold down the command key 176

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which in your case might be the control key 177

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or maybe the option key. 178

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So I know there are different configurations for this 179

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and it might not even work for you. 180

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So please don't ask any question in that case 181

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but for me, I just have to hit command 182

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and then I can double click on multiple words 183

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and then all of them get selected. 184

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So now I have these four multiple cursors here again 185

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and I can simply delete all of them 186

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And right the one that I'm interested in. 187

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so that's the lowercase BMI 188

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and now we get to correct values 189

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And also this conditional logic is correct as well. 190

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And so it is we did actually solve the challenge 191

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and with this we also finished this introduction 192

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to JavaScript objects. 193

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And once again, I really want to congratulate you 194

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for the progress that you're making here. 195

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Great job and really well done. 196

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And I really mean it because I know how hard it is 197

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to stick to a course like this 198

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and to learn a completely new thing 199

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that is probably a bit confusing 200

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for you at this point still. 201

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Just keep in mind that that is absolutely no problem at all. 202

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And actually in the next section I believe, 203

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I have a video about how to learn, 204

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how to learn basically so about learning how to code. 205

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And there's a lot of great tips that I'm sharing there. 206

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So once you reach that, make sure to watch it carefully. 207

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But now anyway, I will leave you to review 208

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this lecture if you want or to move on together with me 209

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to the next video 210

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where we're now gonna start talking about loops.