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Loosely related to the idea of a tuple is the idea of having a couple of specific identifiers global

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constants you might be working within your app which you want to represent as numbers.

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But to which you want to assign a human readable label.

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And for Dad you have to enum type.

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Again that does exist in some other programming languages.

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Javascript doesn't know it though it looks like this is how you create a enum.

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You used to enum keyword which only exists in types called world not in JavaScript.

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They're off to you you have curly braces and then your identifiers and this type which is added by typescript

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gives you an enumerated list.

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So these labels are in the end just translated to numbers starting at zero where you have human readable

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labels you can work with in your code to show you an example.

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Let's go back here to our person with its role.

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I'll copy that code and then comment it out because I'm going to change it a bit and then here I'll

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get rid of that explicit type assignment and instead go back to inference because I'll now change role.

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And now let's say we want to have a admin an author and maybe a read only user the admin should have

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an idea of zero read only user has one author has to now of course we can store that exactly like this

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with these numbers.

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One downside is that we can also add a number for which we might not have a role and if we then later

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in our code try to extract a role and use it if check.

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This might lead to errors and in addition we as a developer have a hard time to understand which role

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is user has lost to the author or was it do you read on the user you might forget this after making

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longer pauses when working in bigger teams and so on.

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So as a developer we might want human readable identifiers something like admin and read only user something

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like that.

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Now of course we could use that we could work with such string values.

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The problem is if we then later need that and they if check we check if person dot role is equal to

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was it read only user or was it one word.

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Was it with underscores.

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You see then we have to remember how we wrote these strings which exact text we have in there because

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this string with the dashes between the words is of course not the same as this string.

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So here we would never make it in their is read only if we tried to compile and print that because well

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the checks simply doesn't yield true.

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We don't have dad as a role on person hence we don't get the output here in a console.

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So string identifiers all have downsides now for such scenarios.

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It's quite common in javascript to define global constants for example admin which can hold certain

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values like numbers or strings both as possible numbers of course can save us some extra code and bits

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and memory and then we might have admin read only an author like this and down there we then just have

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to use that role.

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Now the advantage of that is that we can use this everywhere in our code and therefore here for example

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if I run this code if I compile it and then we let this reload we see as admin here.

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So this works and this is a common pattern in JavaScript.

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Downside is that now again role is inferred to be just a number.

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So we could store any number in there even a number which we don't support.

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And in addition we have to define all these constants.

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We have to manage them.

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This is where a enum can save us work.

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This is totally fine but at enum makes it easier.

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We create a enum with the enum keyword we can name ID roll conventioneers to start with the uppercase

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character because the enum also is a custom type it's your first custom type.

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We're going to write many more in this course.

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This is the first one and then after the name of the type you want to assign to this enum you add curly

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brace just like that no colon no equal sign just curly braces.

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After the name then a semicolon.

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And now in here you can assign your values like admin read only and author and behind the scenes this

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year receives the number is 0 this year.

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Number one this year.

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Number two.

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And then here you can access roll dot admin like on an object you axis your identifier and you can use

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that anywhere else in your code as well.

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Here we can check if the roll is author and then print author.

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And of course we shouldn't see that if I run that now because we assigned a role of admin here but the

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key takeaway is that we did all of that with the help of the enum which assigns labels to numbers.

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We have a look at that in JavaScript so in the compiled code we see does this how it's rebuilt in the

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end it's rebuilt with a if a year so a function which executes itself and roll here simply is managed

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as an object in the end which has admin property a read only property and all through property where

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we then store our no value is here you could say so it's a bit more complex than that but that's what

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types in the end does here to replicate this enum construct in JavaScript code when it compiles the

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code here as a developer we simply have these conveniently created numbers if you hover over them you'll

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see the number which was stored in there and you can use these numbers here in a human readable way

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now for in you're also not restricted to the default behavior let's say for some reason you don't want

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to start with zero as a starting number then you can add a equals sign here after your identifier and

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enter any other number and now admin is assigned to the number 5 and the other identifiers after the

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identifier where you assign a value pick up on that and simply increment this starting value.

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So now we have 5 6 7 instead of 0 1 2 you of course also can assign your own values to all these identifiers

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if you need your own numbers you're also not restricted to numbers you can also go with text here or

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even mix it like I'm doing it here anything goes there but often the default of incrementing numbers

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that start at zero is what you want but if you need a different behavior if you want to use a string

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in here and then a number here and here a number as well or maybe another string then you can absolutely

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do that.

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The advantages you defined it up there and then thereafter you always just refer to your role.

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Type 2 this custom type you created to this custom enum you created and you use that in your if checks

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and your type assignments and you're good.

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That's the power of the enum and it's a great construct whenever you need identifiers that are human

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readable and have some mapped value behind the scenes.