Code Blocks for Specific Tasks: Functions

Functions are reusable blocks of code designed to perform specific tasks.

You create a function by using one or more lines of code enclosed in curly braces { } to form a block, and then you give this block a name.

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function sayHello() {
  console.log('Hello');
  console.log('Nice to meet you');
}

In the example above, the function that prints the messages 'Hello' and 'Nice to meet you' is named sayHello.

The function contains two console.log commands within the curly braces { }, forming a single block.

When the function is called, the code inside the function is executed, printing the messages 'Hello' and 'Nice to meet you' on separate lines.

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function sayHello() {
  console.log('Hello');
  console.log('Nice to meet you');
}

sayHello();
// Hello
// Nice to meet you

The main goal of using functions is to enhance reusability of code.

Once a function is defined, it can be invoked multiple times using its name.

This reduces code duplication and improves maintainability.

In JavaScript, functions are defined by using the function keyword, followed by the function name and parameters.

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

Here, add is the name of the function, and a and b are its parameters.

The curly braces { } contain the code that executes when the function is called, and the return keyword is used to yield the function's result.

Calling a function means executing the code inside it.

To call a function, append parentheses () to the function’s name.

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const result = add(10, 20); // 30

In this example, add(10, 20) calls the add function, and 10 and 20 are the arguments passed to it.

Upon invocation, 10 and 20 are assigned to the function's parameters a and b, respectively, executing the code return a + b and returning 30.

The value 30 returned by return is stored in the constant result.

Parameters are variables used internally when defining a function, whereas arguments are the actual values passed when a function is called.

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function multiply(a, b) {
  return a * b;
}

const result = multiply(2, 3); // 6

For instance, in the multiply function, a and b are the parameters, and the values 2 and 3 are the arguments passed during the function call.