datatypes-in-javascript.md

Datatypes in JavaScript. 😙

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There are primarily two types of datatypes in JavaScript:

➡ Primitives 💫

➡ Objects ☯

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Primitives 💫

The lowest level building blocks in JavaScript are primitives, which include: undefined, null, string, number, bigint, boolean, and symbol. All primitives are immutable.

> typeof  5; // number
> typeof "Mon" // string
> typeof null // null
> typeof true // boolean

JavaScript provides seven different primitive data types:

Data Types	Examples
undefined	A variable that has not been assigned a value is of type undefined.
null	No value.
string	'a', 'aa', 'aaa', 'Hello!'
number	-5, 2, 0.1
boolean	true, false
object	A collection of properties, with key and value pair.
symbol	Represents a unique identifier.

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Objects ☯

Anything that is not a primitive is an Object, or a descendant of it. Objects are collections of key/value pairs and used as the building block for more complex data structures.

typeof {}; // object
typeof []; // object
typeof function () {}; // function (which inherits from object)

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The difference between undefined and null

✅ undefined: It is the default value for any variable which is declared but has no value assigned to it, OR a function which doesn't return anything.

let x;

console.log(x); // undefined

// OR

function meh() {}

console.log(meh()); // undefined

✅ null: It represents "empty" value, which a programmer would assign explicitly.

let x = null;

console.log(x); // null

// OR

function meh() {
  return null;
}

console.log(meh()); // null

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JavaScripts TWO equality operators

JavaScript porvides two equality operators == and ===. Since this is the case there is a lot of confusion

➡ ==: It is called the equality operator. It only compares the data.

➡ ===: It is called the identity operator. It compares both data and the data-type.

Let's understand the the differece between them with an example.

// Exmaple 1
console.log("5" == 5); // true 🤯

//Example 2
console.log("5" === 5); // false 😋

This happens because JavaScript will run a converstion before running the comparision. To handle this you should always use the === operator instead of the == operator.

Lets recapitulate 📝:

➡ There are primarily two types of datatypes in JavaScript: Primitives and Objects.

➡ Primitive data-types can not be mutated, where as Objects can be mutated.

➡ Always use the `===` operator instead of the `==` operator for comparison.

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See Also:

⚫ What is the Truth? 🤥 Read ▶
⚫ Promises 🤝 and Async/Await 🤯 Read ▶