Create simple function in JavaScript

To create a function in JavaScript, you can use the function keyword, followed by the name of the function, and a set of parentheses. The code for the function goes inside curly braces:

function functionName() {
  // code to be executed
}

For example:

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

You can then call the function by using its name followed by a set of parentheses:

greet();  // outputs "Hello, world!"

You can also define a function that takes arguments, which are values that are passed into the function when it is called. For example:

function greet(name) {
  console.log(`Hello, ${name}!`);
}

greet("Alice");  // outputs "Hello, Alice!"
greet("Bob");  // outputs "Hello, Bob!"

You can define as many arguments as you like, separated by commas. The values passed in when the function is called are called “parameters.”

function greet(firstName, lastName) {
  console.log(`Hello, ${firstName} ${lastName}!`);
}

greet("Alice", "Smith");  // outputs "Hello, Alice Smith!"
greet("Bob", "Jones");  // outputs "Hello, Bob Jones!"

Finally, you can use the return keyword to specify a value that the function should return when it is called. For example:

function square(x) {
  return x * x;
}

console.log(square(2));  // outputs 4
console.log(square(3));  // outputs 9