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Let's get started with a ray meters and ray meters are the meters that we can use to operate on the

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arrays.

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For example, let's say I want to remove a record from an array.

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I need a ray method if I want to add record to an array.

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I need a remitted.

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If I want to know how many records are in the array, I need a ray method.

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That is what we are going to talk about in this particular video.

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We have couple of them, so let's take them one by one or one after the other.

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So let me comment out this one and let's use the same data here as our array here.

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So let me comment out this one.

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And now we are making use of this array to do some manipulations.

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So here let's comment.

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I think let me remove this one.

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Even cases to have some one half one code here.

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Okay.

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It is good.

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So I methods.

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Array matters.

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We have couple of them, so let's get started with that.

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All the description we provided in the PDF Guide.

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So don't worry.

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Just follow along and understand the concept that is most important thing.

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So the first array that we will talk about that we will talk about is what you call push.

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Okay.

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So push us element at the end of an array.

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So it is used to add elements at the end of an array.

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So let's say that for this book in future I want to add new book, how am I going to do it?

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Maybe thinking, well, I can come here, have some, come on, then I can add it here.

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But this is not dynamic, meaning I'm doing it manually.

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So for programming it should be dynamic, right?

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Your code should be dynamic.

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Not like one.

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One way of doing things.

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So let me remove that and let's make everything dynamic.

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So how can we add record to an array?

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Using push is as simple as A-B-C or what I need is I will bring in mine arrays, that is books on that.

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If I press dot, I have all these methods that are be taking it through, at least most of them.

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So here the first one is called push.

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Then I want to push what record?

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What data?

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Let's say I want to push in HTML.

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Sorry, I have let's say CSS into it.

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So now if I check my console.

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Here.

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Then I search for books to see that I have the this record you see that I have CCIS at the end of the

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array.

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That is how it works through.

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The push is used to add record at the end of the array.

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So what are some of the use cases here able to push?

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Well, if you get back to back end development, they are a lot of use cases even on the front end.

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Let's say that you want to know how many records are in this book array.

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If at least there are ten records in this array, maybe you can say, can I only add one more book into

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it?

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So first we can make condition and say that, well, if the length or the record in this book is less

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than ten, then I can add a book to repeat because it's not full yet.

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Okay.

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It's not full meaning it's not up to my requirements so I can go back this way.

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And another scenario is that where I push a lot is that let's say, I mean, you are doing a block application

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and then you are doing what is called follow and unfollow user where we see that in some use cases,

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if a user is not following a certain user, we can push the user into an array of followers of that

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follower.

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So that is I mean, a high level is now here, but push is used a lot, so we pay attention to that.

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The next method is what you call pop.

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As the name implies, Pop is used to move an element at the end of the array.

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So for the pop, it doesn't take anything.

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I'll just take in the box.

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Then I will say, Pop, let's pop.

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Champagne.

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See how your popping champagne is, puff when you pop it out.

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Right.

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So if I sip this one now, I want to check the records in the boost array.

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What would be the answer if Pop remove a record at the end of the era and is the last record here?

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Okay, so if I save it and I check for boost, this success will be removed.

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Check it out.

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You see, we don't have Ccaea, but if I did not push pop out this one, I save it.

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If I check it, we see that I'm going to have the CSS which is here.

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Good.

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That is the pop for you.

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The next method is what we call the on shift.

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This name for me is all that descriptive or is the on shift?

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But let's see.

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The meaning on shift simply means that it is used to add record at the beginning of an array.

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Is it?

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I see.

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I mean, on shift.

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You are shifting something, right?

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But on shift, I don't know.

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Well, that is it.

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So we have no option.

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So the next one is what you call the on shift.

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Aren't the works here.

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Throughout confusion.

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Come here.

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So let's say that I want to add a record at the beginning of this recording here.

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You see, the difference is the push is used to add at the end and then on shift add at the beginning

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of an array.

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So here we go.

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So books dot on shift and now I want to shift.

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What book?

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Let me say no.

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See if I check this one.

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You see that?

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I have no idea at the beginning of the array.

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That is the on shift for you.

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You're going to have I mean, a lot of challenges here.

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I mean, a lot of coding challenge, no challenges here.

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Everybody should pay attention.

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The next one is called the shift, right?

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So here the next one going to be shift.

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So a shift is used to remove an element from the beginning of an array.

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So you can see that some differences here.

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Let me show you here.

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Push is used to push record at the end.

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And on shared.

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It's used to our records at the beginning.

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And Pop is used to remove record from from the end and then shift remove record from the beginning.

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You see how the differences are right now.

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So let's say I want to remove MongoDB.

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So let me comment out this one.

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The on shift.

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Let me comment out the push also done with that to the shift.

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So I would take the books away.

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Then I would say shift.

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The shift doesn't take anything.

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So if I save it and I'll check my console, you see that I don't have MongoDB because shift has removed

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MongoDB at the beginning of the array.

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The next array method is what we call the index of so index of remember when when we're treating strings,

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we talk about index of and I say that you will come back because index of operate on arrays, remember.

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So if you have a string of characters, we can split it and then use index of determine where a particular

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string or case.

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So index off retains the index of the first element in an array that matches the specified value.

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So we index of the kind of searching record in an array if it exists where it return true.

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So here index.

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Let's say that I want to search for a record at index one.

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Do you have a record of that?

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Let's see.

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So I would declare variable counts and say result is equal to books dot index of.

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Then I want to check for let's say in HTML.

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So let's check at which index that HTML.

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Okay, you see it?

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Okay.

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At index three, that is zero one, two, this is two and three because this is combined together.

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Okay, let's make it like this one.

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Yeah.

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So zero one, two, three.

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That's why we have the index three.

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So if you get a positive number, it means that it exists.

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But if you get a negative number, it means that what we are trying to search for doesn't exist.

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So let's say I want to search for PHP.

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So if I check for this one, there is no PHP value in my record, so I get what?

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Negative one?

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So negative one simply means that it doesn't exist.

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So let's search for MongoDB.

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Analysis said for that in the zero.

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So let's say our brain in uppercase here let's say for that again so the clue here is that index of

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is also case sensitive meaning that if here is lowercase by the beginning we are searching for uppercase

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going to say please, I don't know you.

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So to avoid this one, you need to I mean, transform the text, all of them to lowercase or to uppercase

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so we can take this array here.

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Okay.

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And then use map to create a new instance of this array.

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And then we are going to transform all the text in the array.

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Then whatever about passing here, I can use the to lowercase transform so to match whatever I have

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my record.

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That's one scenario here and that is the index of for you.

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The next one is going to be the last index of the last index of returns, the index of the last element

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in an array that matches the specified value.

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So let's see.

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So here, let me bring out because my comment is getting longer here.

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So let me bring the record here and let's continue the method.

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The next one is going to be as last.

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Index.

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Of make it so.

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Let's assign or I can quickly console.log like that.

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I would take the books.

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And then at last index of.

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And then our search for, let's say, a HTML.

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No, I get three.

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So you see that it catch at where I mean index 30123.

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If I search for node JS.

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It worked at index one.

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So it retains the last element in an array that matches the specified value.

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So what about include a key?

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The next method is going to be the include method.

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So this method, you are going to use all of these methods and least normally I normally use push most

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often and then include an index of lost index of where it depends on some use cases.

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Okay.

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So what are the include says include returns a boolean indicating whether an array includes a certain

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value the same as using or the index of.

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So the include here which by when to return a true or false, but for an index of it returns a value

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if it exists a negative value if it doesn't exist.

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So here is index or include.

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So I'll bring here as include.

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Now let's see.

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Is it that I get true?

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Because here there is no JS inside the so you have true.

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If I search for let's say no just says such that I get false meaning that this value doesn't exist.

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So using this I mean include here and then the index of this one is more descriptive by where?

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It depends on some use cases.

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Good.

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And then the next step is going to the next array is going to be okay, let me bring this one here and

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this one here.

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So maybe in future you can reference that.

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So the last index for this one, I'm just console.log.

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The answer on the fly.

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Okay.

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That's why I put them into console.log.

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So this one is same as if you're confused about this one.

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I can assign the result, let's say cause as my results that then I can console.log this one by this

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one I just want to console.log it on the fly.

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That's why I put it inside my console.

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Look like that.

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Okay, so now let me I'm done with the include the next one going to be the reverse.

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Remember, reverse is used to reverse the array.

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You may need this one to be able to challenge.

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I may solve the upcoming coding challenge.

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So let's see.

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Let me comment out this one.

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Copy it and put it here.

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Now let me change this one to reverse.

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Reverse.

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That doesn't take in anything like that.

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So if I save it, let's see the reverse value here.

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Now a HTML has become first followed by React and MongoDB is last.

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We see that.

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Now HTML here has become one here first and then react followed by and then MongoDB is the last one.

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So it is used to reverse array.

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The next method is going to be reduce pro.

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This is the crucial method that we're going to use it a lot.

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A lot.

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A lot.

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A lot.

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A lot.

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A lot.

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So what is the reduce.

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Made it.

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Okay.

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So we have a specific section to talk about how we can loop through a race.

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But for the meantime, let's start with the reduce because we may need that one to solve the upcoming

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coding challenge.

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So I think let's postpone that because risk pressure method and take my time to explain to you.

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So let's continue in the next video, guys.