Basic Data Types

In JavaScript, the response to 1 + 1 can be either 2 or 11 depending on the data type. Understanding this requires knowledge of the Seven basic data types or also called primitives in JavaScript: String, Number, Boolean, Null, Undefined, Symbol, and BigInt.

String

Strings represent textual data in JavaScript and are created by enclosing text within quotation marks. You can use either single quotes (”) or double quotes (""). The choice between them is a matter of personal preference. For example:

let greeting = "Hello, world!"

Get started with JavaScript essentials: discover basic data types such as String, Number, and Boolean, and how they affect your code. Learn about semicolons and their role in code clarity, and understand how to use comments to document your work. Explore the browser console for running and debugging JavaScript, and see how to link JavaScript files to HTML using the

Strings can also include apostrophes by adding a backslash \ before the apostrophe or by using backticks “. For example:

// Use Backslash
let message = 'It \'s a sunny day!'
// Use Backticks
let message = `It's a sunny day!`

Strings can be concatenated using the + operator. For example:

let fullGreeting = "Hello, " + "world!" // "Hello, world!"

So, that’s why 1 + 1 can be 11 in JavaScript.

Number

Numbers represent numerical data, you create numbers by writing the number directly.

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In JavaScript, numbers behave like they do in mathematics. For example:

let sum = 1 + 1 // 2
let substracts = 22 - 2 // 20
let multiplies = 22 * 2 // 44
let divides = 22 / 2 // 2
let modulus = 22 % 5 // 2

Boolean

Boolean can only be true or false and are used for logical operations. For example:

let isRaining = false
let isSunny = true

Null and Undefined

Null and undefined both represent the absence of value. undefined typically means a variable has been declared but not assigned a value. null is an assignment value that means no value or no object. For example:

let emptyVariable // undefined
let nullVariable = null // null

Symbol

Symbol is a unique and immutable data type introduced in ES6. Each new Symbol value is completely unique. For example:

let symbol1 = Symbol('symbol')
let symbol2 = Symbol('symbol')

console.log(symbol1 === symbol2) // false

Symbols are rarely used and are meant for very unique cases that you won’t encounter often. You can read more about symbols.

BigInt

BigInt stands for Big Integer, allows you to represent integers larger than 2^53 - 1, which is the limit for Number. For example:

let bigNumber = BigInt(9007199254740991) // 9007199254740991n

Remember that BigInt is not often used unless you work with very large numbers. You can read more about symbols.