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Welcome to Coding Challenge number three.
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And this is gonna be a quick and easy one.
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So all I want you to do is to rewrite
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the 'calcAverageHumanAge' function
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that we wrote in the previous challenge.
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Now the difference here is that this time,
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you should use an arrow function
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and you should use chaining.
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Now to make this chaining work,
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just keep in mind the second way that I used
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in the last challenge to calculate the average.
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Then, as always, use this test data here
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to try out your function.
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And so I'll see you here in a minute,
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or five minutes maybe, once you're done.
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Now all right, so let's grab the code here
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from the previous one.
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So there's no need to just rewrite everything.
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So let's get rid of all the comments here,
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all the console.logs.
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And so let's save it here,
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and then rewrite it as an arrow function.
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So it still takes in the ages,
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and now what it returns is simply the ages,
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then dot, this map,
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so calculating the human ages.
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Okay, and then on the result of that,
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we filter for only the adult docs.
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So when the age is greater than 18.
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So this is what we have for now.
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Let's call this one here two.
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Okay. And so for now this is the two erase that we have
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one for each function call.
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But now let's then also calculate the average.
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And so for that all we need to do is to chain
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this method of calculating the average.
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That he showed you in the last lecture,
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or actually in the last challenge.
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So pasting that here.
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And so now we get the exact same results as before,
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and that's actually already it.
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Now what's really important to notice here,
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is that this is actually really the only way
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of calculating the average now.
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So basically dividing the age by the length
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of the current array immediately here
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in each of the iteration.
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So remember that in the last challenge,
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I first simply added all the values together.
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And then afterwards I divided it by the length of the array.
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So in this case, by the length of the adults array.
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However, that would not work in this case.
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Because there would be no way of knowing the length
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of the adults array.
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So of this result here, right?
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Because we haven't stored it anyway.
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And so we couldn't do like this, like adults.length, right?
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This wouldn't be possible
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because adults here does not exist anywhere.
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And therefore we need to take that length
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from this input here.
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So from this fourth parameter,
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which gives us access to the array,
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on which the method is called.
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And that's the reason why I showed you this way here,
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in the last lecture.
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Because yeah, again this is the only way
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in which we can now calculate this average,
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unless we wanted to do it in two steps.
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But my instruction here
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was to really do it all with chaining.
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And so this is the way to go then.
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All right, so make sure you understand
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really why and also how this one here works.
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And then let's already move on to our next method,
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which is gonna be defined method.
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So another really cool one.
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So I can't wait to see you there.
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