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And this video I'm going to go over creating the solutions to this array problem set starting from scratch

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.

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So the first one we have is print referrers.

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So before we start.

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And when I get my files set up correctly I already have an aged him file.

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I just called that solution that HMO.

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I'm going to include a script tag source equal to solution that J S and then I need to create that file

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.

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So let's save that solution.

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Yes.

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And as always I'd like to start with my council but log connected.

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Let's go.

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Open this up in the browser.

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Open up the console and we see are connected.

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All right.

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So let's start with print reverse.

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So print reverse is a function.

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So I'll start by defining the function print reverse which takes a single argument and array.

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I'll just call it a r r and all we need to do is loop through the array.

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Except we want to loop backwards from the end of the array to the beginning and then we'll just call

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its var log each item.

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So a foreach isn't going to be ideal here.

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We're going to use a for loop which is a little more flexible in the order that we traverse the list

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.

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So for var I instead of starting at zero we're going to start it at the end of the array.

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So var equals array don't like minus 1 and we have to add that minus 1 because the length is always

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one greater than the greatest index.

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So it's spaced out a bit.

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Next we're going to keep going.

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While I is greater than equal to zero.

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And then lastly we're going to minus minus.

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So I will start at.

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In the case of print reverse of this array 3 6 to 5 I will start at this index which would be three

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and we'll print out the log array if I so that will print out 5 and then you subtract 1 from I and print

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out a array of I gives us 2 and then 6 and then 3 and the last time through is equal to zero.

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So we print out three and then we're done.

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So let's take a look.

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I'm going to call this print refers with this array.

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Run it in the browser and you can see we get 5 to 6 and 3 which is what we expected.

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Five to six and three.

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Let's move on to the next problem.

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So the next problem is is uniform which takes an array as an argument again and returns true.

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Only if all the elements are exactly the same.

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So I'm going to start by just writing a note that this is where is uniform starts because this file

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will be pretty full by the end of this.

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So I just want to make it clear.

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So let's start by defining our function is uniform and it's going to take a single array.

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So the way that I'm going to solve this I'm going to make a variable equal to the very first item.

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So in this case 1 and then I'm going to loop through the array and compare that first item to every

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other item and if at any point they're not the same then we're going to return false and just end the

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entire function.

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But if we make it to the end that means that every item is the same.

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So we can return true.

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So I'm going to start by making my first variable var first is equal to the first item.

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Then I'm going to loop through the array.

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So I'm going to use a for loop here and there is a reason I'm not using a foreach which I'll explain

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after this.

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So I'm going to start looping through I less than Array don't like I plus plus and I'm just going to

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check if array high is not equal to first.

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That means that our array is not uniform.

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So I will return false.

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And then at the very end of my array if we make it through the whole loop I can return true.

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There is one small optimization here which is I'm currently comparing the first item arrays zero to

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the first item.

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The very first time through the loop.

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If I start says 0 and checking is erase the row equal to first.

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So I don't want to do that.

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I'm just going to start it at index 1.

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Let's test it out.

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Refresh our page is uniform of the array 1 1 1.

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That's true.

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But how about 1 1 2.

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That's false and two went.

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That's also false.

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OK.

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So I mentioned that I didn't want to use a for each.

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And the reason behind that is that if I wrote a foreach comment this out and instead of a for loop here

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if I did a red dot for each function and I call it element and I'm going to check if element is not

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equal to First

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I will return false.

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This is exactly the same logic except we added in a foreach instead of a for loop.

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We have a problem and the problem is that when I return false here this only returns out of the first

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function which is right here.

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So it doesn't exit all of its uniform it just exit out of the first function which then brings us to

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this level and then it just runs the next line which is returned true.

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So rather than have to deal with the work around here I'm just going to use a for loop because it's

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much simpler but I want you to understand what the problem is.

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So to sum that up again I return instead of one function.

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It only peels back one layer so it only returns that exact function and then the next function that

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it's inside of it still finishes its execution.

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So I will come with this one out and let's just leave this one as our real solution.

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Next up we have some array.

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So some array takes a single array and it sums every item inside of it.

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So we're going to start with my comment some array and I'm going to declare the function some array

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takes a single array.

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And in this case we need to make a variable to hold the total.

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And then we need to loop through the entire array and add to that total.

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So I'll start with my variable total equals zero.

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And then I'm going to do it for each.

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So array for each.

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And I could just do a regular for loop and I'm just going to call this element and I'm just going to

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add in to total every time.

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So total plus equals elements.

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And then the end return total and that's all I have to do.

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So start total zero loop through the array take every element and added into total and then return total

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at the end.

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Let's test it out.

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Let's try doing some array on the array.

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One two three and I get six.

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And how about 10 10 10 and you get 30.

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OK so that's some array.

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The last one here is determining the max element in an array of numbers.

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So I'm going to add my comments in first.

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We're going to work on Max here and I'm going to define that function first.

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So function Max takes a single array again and the logic here is that we're going to have a variable

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to keep track of the maximum and we'll just started as the first element by default and then we're going

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to loop through every other item and compare that to the current maximum.

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And if it ever is greater than the current maximum then that element is our new maximum.

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And then we return that at the end.

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So I'm going to start var Max equals array 0 and then I'm going to loop through the array and just for

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variety's sake I'm going to use a for loop.

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So for var I equals zero.

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And actually you can start it at 1.

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Because we're already using a ratio for the same reason they can start this one at 1.

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So I started at 1 4 equals zero.

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I have less than a radar link plus plus.

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And all I want to do is check if array of I.

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So if the individual element is greater than the max then Max is now equal to Array.

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So this will constantly change its value or potentially change its value if it encounters a new maximum

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.

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So in this exercise here one two three at the very beginning.

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One is the max.

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And then we go through the loop and we compare it to two.

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Two is greater than one.

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So two is the new maximum.

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And then that repeats three is greater than two.

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So three is a new maximum and the last line that we're missing is once the loop is done we just return

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Max.

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And what should be good to go.

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So let's try this out refresh and let's try running max on 1 2 3 and we get three.

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Now let's try adding 20 in the middle and we get 20.

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And lastly let's play with a negative number and make sure that works.

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And we still get 20.

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OK.

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So we have four solutions here.

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All of them needed to use a loop we used for each and some of them.

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We used a for loop and some of them and all of them.

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We practice a race.

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Awesome.

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So next up we're going to learn about our next data structure and javascript's which is the object