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Javascript Data Types

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Rockey Biswas
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3 min read

In Javascript, there are total of 8 data types.

String, Number, Boolean, BigInt, Undefined, Null, Object, and Symbol.

We can put different data types in the same variable. A variable can be a string and in another line, it can become a number. Javascript is a dynamically typed language that allows us to do that.

1. String

string in Javascript is surrounded by quotes. And they are immutable.

In Javascript, we can write strings in different ways.

Double Quotes

let doubleQuotes = "Hello World";

Single Quotes

let singleQuotes = 'hello World';

Backticks

let backTicks = `hello World`;

A special feature of backticks is it lets you use variables and expressions inside a string by wrapping them in ${}

let str = `hello`;
let special = `${str} World`;

console.log(special); //hello World

2. Number

number type lets you store integer and floating point numbers.

let integerNum = 123;
let floatingPoint = 123.4;

You can do various math operations with numbers e.g addition, subtraction, multiplication, and division. You can store special numeric values too like infinity, -Infinity and NaN which is short for Not a Number.

3. Boolean

The boolean type has only two values true and false. true means correct and false means incorrect.

let a = 3;
let b = 4;
console.log(a > b); //false

4. BigInt

In Javascript, a number type cannot safely store a number larger than (253-1) or less than -(253-1) . To store a bigInt value append n to the end of an integer.

let bigInt = 3453453453453453463465465654654n;

5. Null

null type in Javascript is a special data type as its name suggests. It means null, nothing, empty.

let nullType = null;

6. Undefined

Just like null undefined is also special. Any variable which is declared but isn't assigned any value is undefined.

let undefinedValue;
console.log(undefinedValue); //undefined

7. Object

Objects are keyed collections of various data. The above data types we learned are called primitive data types because they can store only one type but the object is a little different. Objects can store values of different types.

let obj = {
  name: 'John', //string
  age: 30, //number
};

```
You can only use ```string```, and ```Symbols``` as object property keys.
Using any other type gets converted to a string.

```
let obj2 = {
  name:  'John',
  1: 30,
  };

console.log( obj2['1']) //30

console.log(obj2[1]) //30 same as '1';
```
## 8. Symbols

Symbols are used to make unique identifiers. 
Symbol type  can be made using ``` Symbol()```
we can give descriptions in Symbols.
```
let sym = Symbol('description');
```

Even if two symbol store the same description they are not equal.

```
let a = Symbol('id');
let b = Symbol('id');
console.log(a === b); //false
```
JavaScript