JavaScript Tutorial: Functions and JSON Objects

1. JavaScript Functions

Definition: A function is a reusable block of code that performs a specific task. Functions help in writing cleaner and more organized code by allowing developers to define a set of instructions that can be executed multiple times with different inputs.

Defining a Function

function greet(name) {
    console.log("Hello, " + name + "!");
}

Calling a Function

greet("Alice");  // Output: Hello, Alice!

Function with a Return Value

function add(a, b) {
    return a + b;
}

let sum = add(5, 3);
console.log(sum);  // Output: 8

Exercise on Functions

Create a function called calculateArea that takes two parameters (width and height) and returns the area of a rectangle. Call the function with different values and display the output in the console.

2. JavaScript JSON Objects

Definition: JavaScript Object Notation (JSON) is a lightweight format used to store and exchange structured data. It is commonly used for transmitting data between a client and a server.

Example of a JSON Object

let person = {
    "name": "John",
    "age": 30,
    "isStudent": false
};

console.log(person.name);  // Output: John
console.log(person.age);   // Output: 30

Converting JSON to a JavaScript Object

let jsonString = '{"name": "Emma", "age": 25}';
let personObj = JSON.parse(jsonString);

console.log(personObj.name);  // Output: Emma

Converting a JavaScript Object to JSON

let car = { brand: "Toyota", model: "Camry", year: 2022 };
let jsonCar = JSON.stringify(car);

console.log(jsonCar);  
// Output: {"brand":"Toyota","model":"Camry","year":2022}

Exercise on JSON Objects

Create a JSON object representing a book with properties such as title, author, and year. Convert the object to a JSON string and log it to the console.

3. Combining Functions and JSON Objects

Function That Returns a JSON Object

function createStudent(name, age, course) {
    return JSON.stringify({
        "name": name,
        "age": age,
        "course": course
    });
}

let studentJson = createStudent("Mike", 22, "Computer Science");
console.log(studentJson);

Function That Accepts JSON as Input

function displayStudent(jsonData) {
    let student = JSON.parse(jsonData);
    console.log(student.name + " is enrolled in " + student.course);
}

let studentInfo = '{"name": "Lily", "age": 21, "course": "Mathematics"}';
displayStudent(studentInfo);

Final Exercises (Combining Functions & JSON)

1. Create a function called createMovie that accepts title, director, and year as parameters and returns a JSON object. Convert this object into a JSON string and log it.

2. Create a function called parseMovie that takes a JSON string representing a movie and logs the title and director.

Conclusion

Functions provide a structured way to write reusable code, improving efficiency and readability. JSON is a widely used data format that facilitates data storage and exchange. Combining functions and JSON enables dynamic data generation and processing, making it an essential technique in modern web development.