This is a brief overview of JavaScript functions. I will discuss how functions are defined, as well as explain how functions are called in order to use them. Along with the provided examples, this will give you a better understanding of how to create and use functions in JavaScript.

Defining Functions

There are two ways of defining functions in JavaScript: function declarations and function expressions.

When you declare a function (called a function declaration), you use the function keyword, followed by the name of the function that you give it. Next, comes a list of parameters that the function needs to perform its task (a function can also have no parameters). These parameters are put inside of parentheses and are separated by commas if there are more than one parameter. If the function has no parameters, a set of empty parentheses is used. Finally, the tasks that you want the function to perform are written inside curly braces. A group of statements written inside curly braces (in this case, the tasks that you want the function to perform) is called a **code block. **In the following example, the function contains only one statement, which is alert("Hello!");. This is an example of a function declaration:

function greeting() {
  alert("Hello!");
}

In this simple example, the name of the function that follows the function keyword is greeting. Next, we have parentheses with nothing inside, meaning this function has no parameters. Finally, we have alert("Hello!"); inside the curly braces. This is the task that this function performs. In other words, when this function is called (more on this below), we will get an alert message saying, “Hello!”

In this first example, the function does not need any specific information to perform its task — it has no parameters. It just gives us an alert message. However, sometimes a function needs specific information to perform its task. In this case, we need to provide parameters when we declare the function. We give each parameter a name, and in a function, these parameters act like variables. Here is an example of a function with the parameter of name:

function greeting(name) {
  return name;
}

In this function declaration, we have a parameter of name. So, since the function has a parameter, this means that the function needs this information (name) to work. And the task that this function performs is return name;. In other words, the return statement stops the execution of this function and returns the value of name.

In this next example, the function has two parameters: name and adjective. This means that this function needs both of these parameters to work. And the task that this function performs is return name + " is " + adjective + ".";. In other words, it will return a string that includes the values of name and adjective.

function greeting(name, adjective) {
  return name + " is " + adjective + ".";
}

The second way to define a function is by using a **function expression. **In a function expression, the name of the function is usually omitted (a function with no name is called an anonymous function). In a function expression, the function is stored in a variable, after which, the variable can be used as a function. This is an example of a function expression:

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