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Writing a Function in JavaScript

Computer with Code

In JavaScript, functions are blocks of reusable code. They allow you to bundle functionality, make it more readable, and avoid repetition. Here’s a brief tutorial on writing an arrow function in JavaScript.

1. Basic syntax

const functionName = (params) => {
  // code to be executed
}

const: const should be used whenever a function expression is assigned to a variable.
The function name: The name you choose for the function.
Parameters: Optional comma separated parameters. This is the data passed into the function. If there are no parameters, the () is still required.
The arrow syntax: Indicates that this will be a function.
The body: The statements that make up the function itself. Surrounded by curly braces.

Example:

const greet = (name) => {
  console.log("Hello, " + name + "!");
}

Tip: Functions often perform actions, so naming with a verb can make it clear what the function does. Examples include fetchData( ), calculateArea( ), or printReport( ).

2. Calling a function

To execute the function, you call or invoke it by using its name followed by parentheses.

Example:

greet('Alice'); // Outputs: Hello, Alice!`

3. Return values

Functions can process data input and output a value using the return keyword.

Example:

const addNums = (numA, numB) => {
  return numA + numB
}

const total = addNums(2, 4);

console.log(total) // Expected value: 6

For more information on functions and how they are used in JS, check out the MDN docs.