Primitive data types in JavaScript

Published at Oct 30, 2024Updated at Oct 30, 20245  minutes read

In every programming language you will find some primitives values. It's not different in JavaScript, we have 7- number, string, boolean, bigint, null, undefined and symbol. Every one having a different case usage. In this article I gonna show you every Javascript primitive values and its usage case, but first what is a primitive value?

Definition

In Javascript, a data type is considered primitive value if immutable and is not an object and has no methods or properties. You can never change a primitive value in Javascript, for example:

jslet a = 'hello'
let b = a
console.log(b) // "hello"
 
b.substring(2) // "llo"
console.log(b) // "hello"
console.log(a) // "hello"
 
let c = [3]
let d = c
c.push(1)
console.log(c) // Array [ 3, 1 ]
console.log(d) // Array [ 3, 1 ]

In the example above, we can never change the primitive value string hello no matter how many methods we do in b, but is not the case of array c and d, when we push item to d, automatically pushes to c too, so is mutable.

Primitives values are super important to know, independently of the language used, every one has a critical importance and usage case. For this reason, we're gonna explain each one that exists in JavaScript.

type number

In JavaScript, Number is a primitive data type used to represent numerical values. It stores 64-bit floating-point numbers following the IEEE 754 standard, which supports double-precision. This makes it versatile for handling integers as well as decimals, and it's the primary type for representing numbers in JavaScript.

Number accepts almost all operators. An interesting fact is that JavaScript handles somethings that would be consider error in other programming languages, we will see more in the next topics.

An important aspect of numbers in JavaScript is that when you perform an operation that is not possible, such attempting invalid operations between types (like multiplying strings), the result will be NaN, which stands for 'Not a Number' and indicates an error in the computation.

jsconst n = 1
const n2 = 2
 
console.log(n + n2) // 3
console.log(n - n2) // -1
console.log(n * n2) // 2
console.log(n / n2) // 0.5
console.log(n % n2) // 1
console.log(n === n2) // false
 
console.log('text' * 'text') // NaN

type string

A String is a sequence of characters used to represent text in JavaScript. It allows for the storage and manipulation of textual data, making it essential for handling words, sentences, and other character-based information. Strings have a wide range of use cases due to their versatility in representing and manipulating text, making them one of the most frequently used data types in JavaScript.

JavaScript has a particularly behavior- If you use the sum operator with some string there will be no error as would happen in other programming languages, instead JavaScript handle this by transforming the result in a string by concatenating the values.

jsconst s = '1'
const s2 = 'text'
 
console.log(1 + s) //  11
console.log(false + s2) // falsetext

bigint

BigInt is used to store integers beyond JavaScript's safe integer limit (Number.MAX_SAFE_INTEGER). While powerful for handling very large numbers, it is rarely needed in typical small-medium applications.

jsconst maxSafeNumber = Number.MAX_SAFE_INTEGER // 9007199254740991
const beyondMaxN1 = maxSafeNumber + 1 // 9007199254740992
const beyondMaxN2 = maxSafeNumber + 2 // 9007199254740992
 
const bigN = 9007199254740991n
const beyondMaxBigN = 9007199254740991n + 2n // 9007199254740993n

boolean

A Boolean is a logical data type that can only hold one of two values: true or false. It is commonly used in conditions and decision-making statements.

Those values can be represented in other forms like binary, 1 represents true and 0 represents false. This means that, in Javascript you can make operations with those values.

jsconst isDeveloper = true
const isLastType = false
 
console.log(true + 2) // 3
console.log(true - 2) // -1

undefined

undefined is a default value automatically assigned to variables that have been declared but not yet given a value, or to function parameters that have no corresponding arguments.

jslet value
const value2 = undefined

symbol

A Symbol is a unique and immutable primitive value that can be used as a key for properties in an object, ensuring property names do not conflict.

jsconst sym1 = Symbol()
const sym2 = Symbol('desc')
const sym3 = Symbol('desc')
 
console.log(sym2 === sym3) // false

null

A null value represents a reference that intentionally points to a nonexistent or invalid object or address, indicating the absence of any value.

In operations, you can treat null as 0 since many calculations can be performed by substituting null with 0 without affecting the outcome.

jsconst value = null
 
console.log(2 + null) // 2
console.log(2 * null) // 2

Conclusion

In this article we saw all the primitive data types that exists in JavaScript. This article was short, but I hope you like it. Have a nice day. 😎✨✨✨😎

References

Mozilla Developer. Access at

About the author

Profile of Felipe Scherer
Written by:

Felipe Scherer

- Software Engineer

Hello. I currently working as developer for more than 2 years coding sites, apps and games. In the free time I like to write articles to help people get started in this incredible world of coding. Feel free to explore my Github and use my public code 😊. Don't forget to follow me on my socials. 🌟

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I am gonna go though all of them, but be aware my favorite is the last one- By creating a plugin, so if you want, just skip to here ## Arbitrary values-properties-variants Tailwind is built for really hard customization, and that’s so true, you can literaly create any class just combining some prefix or sufix and the compiler will generate for you the classes for build. So, Why we avoid this approach when dealing to customization? The answer is because this goes agains the reusability concept of Tailwind, and if you use more than one that that arbitrary value, I recommend to create a custom utility for it. <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/76b33e7a-bd3f-4940-aabd-e3232034fc7b" name="Arbitrary property Tailwind example" alt="code example of tailwind arbitrary using a color of background" /> <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/9994a2a8-a1df-4be8-813a-759d7ea15e64" name="Build file " alt="Build file showing the arbitrary property became other class" /> ## Customizing the theme If you want to change the properties already build in, like the font-size or color, it’s perfect and really easy to do just customizing the Tailwind theme file. <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/3fcdaf65-9624-4966-8ccd-49aa74daf8c1" name="tailwind.config.ts" alt="Creating a class my-blue in Tailwind file" /> <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/61559e23-be18-43ea-a0a5-04dc0fbca834" name="Code example" alt="Using the custom classes created in a div" /> <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/810e5dfc-70f1-4505-88df-bc1a25c8653d" name="Build file- This may looks weird, but is the same blue I configured, but just with some Tailwind optimization." alt="Build file showing that Tailwind handle better using theme" /> The problem is when you need to create a custom component class, like you repeat that same classes and that became redundant and hard to read. <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/5920d701-17f9-476e-8df4-c5c3024c4594" name="Example of reduntant classes" alt="File showing a lot of container with same classes" /> Isn’t better having just one class like `hello-world-container`? Yes. ## @layer and @apply directive There is a way to add custom classes using some Tailwind directives in CSS files. Like this: <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/53c6e419-42b5-472e-a321-1af95569e58b" name="Example of reduntant classes" alt="File showing a lot of container with same classes" /> You can literaly put any CSS valid property just like the way you would do in normal CSS, but noticed I put the classes inside some directives, why? Tailwind is composed by layers that can be overwritten, eg. You have a base style for your button but you want to change it’s color just in one component, to make that you will need to overwrite it, in normal CSS you will probably use !important, and trust me in my experience if you had use !important, probabily there is something wrong with your code. So use layers with wisdom. I recommend using: - [@layer base](https://tailwindcss.com/docs/adding-custom-styles#adding-base-styles) for tag styles, like I used in the example for tag `code`. - [@layer components](https://tailwindcss.com/docs/adding-custom-styles#adding-component-classes) for classes that has more than one style like the `hello-world-container` which has **display: flex;flex-direction:column;justify-content:center;background-color:purple;padding:1rem**. Most customization you will need is gonna be made here. - [@layer utilities](https://tailwindcss.com/docs/adding-custom-styles#adding-custom-utilities) is the highest priority, so use carefully. I recommend using just for one single property like **transparent:background-color:transparent**. This will mostly be used for classes that do not exist in default Tailwind. Well, so we learned about the @layer directive, but what is that @apply in the example? This is a way to use your Tailwind token in the styling file. For build does not matter if you use the **hello-world-container** or **hello-world-container-2**, both produces the same result, so @apply helps your code readbility. Using directives may seen the best way to create custom classes in Tailwind, but as I said in the beginning of the article, this is not my favorite way. I prefer much more creating a custom plugin. ## Why I do not like Tailwind directives like @layer and @apply Fist I need to say why I love the experience of working with Taiwlind insted other CSS framework similar like Bootstrap. Tailwind has been investing not just in optimizations and fast files, but in development experience too. Tailwind has a very nice VSCode plugin called [Tailwind Intellisense](https://tailwindcss.com/docs/editor-setup#intelli-sense-for-vs-code) I personally do not recommend you use Tailwind without this plugin. One thing it changes is when you hover a class, it shows what is that CSS equivalent, is literally required for me and I do not see me not using it. <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/9b5e1959-3c80-4589-867c-47b0fdf40e48" name="Tailwind VSCode Intellisense showcase" alt="Print showing when hovering the class has a popup showing CSS equivalent" /> You know, when you create custom classes, you need Tailwind Intellisense to recognize it, but I never found a way to make recognize directives like @layer. When creating custom classes like that, you do not have the hover preview :( This is unacceptable, specially because custom classes do not exist in Tailwind Docs, is the most important classes to have a register and a easy way to check the CSS equivalent. So going though Github Issues and making a lot of testing. I probably have the best solution to create custom classes in Tailwind. ## Create custom plugins As you can see there are a lot of ways to customize you styles in Tailwind, but there is superior way to customize and still get the Tailwind Intellisense working for us, it’s called 🪽 Plugins 🪽. What is and how we implement? <Blockquote cite="https://en.wikipedia.org/wiki/Plug-in_(computing)"> is a software component that adds a specific feature to an existing computer program </Blockquote> So in [Tailwind](https://tailwindcss.com/docs/plugins) is not diffent, plugins are a way to modify the base of Tailwind, you can do a lot of it, but in this article I just gonna show how you can use to create custom classes styles. Every Tailwind project has a **tailwind.config.js** or **tailwind.config.ts** which has all of Tailwind’s configuration, including the **theme** from earlier, but what we want is the **plugins** <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/27b51eae-d5a0-4c14-81cf-19c97aa76398" name="tailwind.config.ts" alt="tailwind.config.ts file" /> You will need to use a function from Tailwind called `plugin`. I highly recommend using Typescript, for its typing features, which helps a lot, but of course you can use Vanila Javascript too. <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/e42b46ba-2710-4575-81b4-6ad8e864e30f" name="Plugin function" alt="Plugin function" /> In it’s parameters you put what you want to create. For this article, we want a component, so we use the addComponent param. <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/bee18037-70d5-435f-810f-fa6876a62629" name="Plugin function add components" alt="Plugin function add components" /> Now just add the class name and the styles like CSS or (CSS Style Declation)[https://www.w3.org/TR/cssom/#the-cssstyledeclaration-interface] (backgroundColor insted background-color). <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/5a6db547-3f58-4eca-98ce-c5564885fbd6" name="Custom class made by plugin example" alt="Custom class made by plugin example" /> And there you go, now you have the hovering effec from Tailwind Intellisense :) <Img src="https://github.com/fescherer/fennec-tales-blog/assets/62115215/688da377-c59e-4cd2-ba24-b02499d4da25" name="Class in action" alt="Print showing when hovering the custom class made by plugin, showing the equivalent CSS" /> ## More dev experience Here's an additional tip to elevate your Tailwind development experience: consider using the [eslint-plugin-tailwindcss package](https://www.npmjs.com/package/eslint-plugin-tailwindcss). This ESLint plugin offers various features to help you write cleaner and more maintainable Tailwind code. ## Summary This article explored various methods for creating custom classes in Tailwind CSS, emphasizing the importance of a positive development experience. By leveraging Tailwind plugins, you can create custom styles while maintaining IntelliSense support and overall code clarity. This approach empowers you to extend Tailwind's capabilities while keeping your development workflow efficient and enjoyable. Thanks for reading see you in the next article, have a nice day 😊