JavaScript Variables and Data Types

In this notebook, we will explore different types of variables and data types used in JavaScript. JavaScript is a dynamically typed language, which means that variables do not need to be explicitly declared with a type. The type of the variable is determined by the value assigned to it.

Types of Variables in JavaScript:

  • var: Declares a variable, optionally initializing it to a value.
  • let: Declares a block-scoped local variable, optionally initializing it to a value.
  • const: Declares a block-scoped, read-only constant.

Data Types in JavaScript:

  • Primitive Data Types:
    • String
    • Number
    • Boolean
    • Null
    • Undefined
    • Symbol
  • Non-primitive Data Types:
    • Object
    • Array
    • Function

Naming convention in JavaScript

The convention in JavaScript is different in Python on its use of camelCase for variables, functions, and mehods; verus Python usage of snake_case.

  • camelCase is used for variables, functions, and methods.
  • PascalCase is used for class names and constructor functions.
  • UPPER_SNAKE_CASE is used for constants.

Strings in JavaScript

A string in JavaScript is used to represent textual data. Strings are created by enclosing characters within quotes (single or double quotes).

Example:

In this example, we will declare a string variable and print it to the console.

%%js
// 1. Strings
let name = "Arhaan";
console.log("String: ", name);
element.append("String: " + name + "<br>");

<IPython.core.display.Javascript object>

Numbers in JavaScript

JavaScript has only one type of number. Numbers can be written with or without decimals. They can be integers or floating-point numbers.

Example:

In this example, we will declare a number variable and print it to the console.

%%js
let age = 25;
let height = 5.9;
console.log(age);   // Output: 25
console.log(height); // Output: 5.9



<IPython.core.display.Javascript object>

Booleans in JavaScript

A boolean represents one of two values: true or false. Booleans are typically used for logical operations.

Example:

In this example, we will declare a boolean variable and print it to the console.

%%js
let isStudent = true;
let isGraduate = false;
console.log(isStudent);  // Output: true
console.log(isGraduate);  // Output: false



<IPython.core.display.Javascript object>

Undefined in JavaScript

A variable in JavaScript that has been declared but not assigned a value has the value undefined.

Example:

In this example, we will declare an undefined variable and print its value.

%%js
// 4. Undefined
let uninitialized;
console.log(uninitialized); // Output: undefined



<IPython.core.display.Javascript object>

Null in JavaScript

The null value represents the intentional absence of any object value. It is often used to indicate that a variable should not contain any value.

Example:

In this example, we will declare a null variable and print its value.

%%js
let emptyValue = null;
console.log(emptyValue); // Output: null



<IPython.core.display.Javascript object>

Symbol

A unique and immutable data type used primarily as object property keys.

%%js
// Creating a unique Symbol
let uniqueId = Symbol('id');

// Outputting the Symbol
console.log(uniqueId); // Output: Symbol(id)




<IPython.core.display.Javascript object>

Arrays and Objects in JavaScript

Arrays:

Arrays are used to store multiple values in a single variable. Each value is called an element, and arrays can store values of any type.

Objects:

Objects are collections of key-value pairs where each key (also called a property) is associated with a value. Objects are the most important data type in JavaScript. They are also called JSON Objects and are similart to Python dictionaries.

Example:

In this example, we will declare an array and an object and print them to the console.

%%js

//Arrays
let colors = ["red", "green", "blue"];
console.log(colors); // Output: ['red', 'green', 'blue']

//objects
let person = {
    name: "John Doe",
    age: 25,
    isStudent: true
};
console.log(person); // Output: { name: 'John Doe', age: 25, isStudent: true }

//fumction 
function greet(name) {
    return "Hello, " + name + "!";
}
console.log(greet("Alice")); // Output: Hello, Alice!



<IPython.core.display.Javascript object>