Original subtitles

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Do you remember how we chained array methods 2

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one after another, for example filter map and reduce? 3

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So by chaining these methods, 4

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we could first filter an array, 5

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then map the result. 6

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And finally reduce the results of the map, 7

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all in one line of code. 8

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And we can actually implement the same ability 9

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of chaining methods in the methods of our class. 10

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And so let's go do that now. 11

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And actually, this is extremely easy to do. 12

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So all we have to do is to return the object itself 13

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at the end of a method that we want to be chainable. 14

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So let's say that we wanted to do this. 15

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So let me take that away from here. 16

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So chaining. 17

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So let's say we wanted to do account, 18

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and then deposit, 19

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let's say, 300. 20

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And then right afterwards, we wanted 21

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to deposit again on the same account. 22

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So we would like to call deposit again, right away, 23

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let's say 500 this time. 24

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And then immediately after that, 25

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let's say we want to withdraw 35. 26

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Maybe we also want to request a loan in the middle of this. 27

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So request loan, let's say 25,000. 28

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And then finally, we want to withdraw some more, 29

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let's say 4000. 30

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So right now, this is not gonna work. 31

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So let's see the error. 32

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And so the problem here is that... 33

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this one here will work. 34

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But this will then return nothing. 35

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Because let's see, 36

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the deposit method does return undefined 37

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because we're not returning anything explicitly here. 38

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And so then undefined gets returned. 39

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And so then here, in this next one 40

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we are trying to call the deposit method on undefined 41

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which is the result of all this. 42

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And therefore we get exactly that error here. 43

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So what we need to do is to call deposit 44

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actually on an account. 45

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And so what we want is for the result of this year 46

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to be again the account, 47

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right? 48

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And so let's do that. 49

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So all we have to do is return... 50

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this. 51

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Because this is of course, the current object. 52

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And now we do the same on all of them. 53

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Okay. 54

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And here the same. 55

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And that's it. 56

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So returning this 57

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will essentially make the method chainable. 58

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And this makes most sense, in methods 59

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that actually set some property. 60

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And so all of the three, that we just did this, 61

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actually do that. 62

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So this one sets the movements here. 63

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This one, actually two, 64

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and this one also changes the movement array. 65

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And so all of these, basically set some property. 66

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And so these are then very useful to make chainable. 67

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So let's see now. 68

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And... 69

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Well, we get no error, 70

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and we get loan approved. 71

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So that means that probably everything worked here. 72

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So let's take a look at our account here. 73

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Actually, let's call account getMovements. 74

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So that's why we have this method in the public API. 75

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And so indeed, all the deposits and withdrawals 76

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that we just did, are now in this Movements array. 77

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Great. 78

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So with this, you have yet another tool in your toolbox now. 79

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So experiment a little bit with this on your own. 80

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And maybe also when you start writing your own classes. 81

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All right. 82

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So with this one 83

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I actually showed you all there is 84

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to show about Object Oriented Programming in JavaScript. 85

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So what a long section here, but also a beautiful one, 86

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if you ask me. 87

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Now, just to really wrap up this section. 88

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Next up, I have a nice overview of the entire class syntax 89

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and then one final coding challenge.