Functions are blocks of code that perform a specific task. They allow for the reuse of code and help to organize and structure programs. Functions can accept inputs, called parameters, and return outputs, making them useful for writing efficient and modular code.
To define a function, you use the keyword "function" followed by the name of the function and a set of parentheses. Inside the parentheses, you can specify any parameters that the function will accept. After the parentheses, you use curly braces to enclose the code that makes up the function.
A function declaration is when you define a function using the keyword "function" followed by the name of the function and a set of parentheses. This allows you to call the function before it is defined in your code. A function expression is when you assign a function to a variable, which can then be called like a regular function. Function expressions are typically used for anonymous functions or when you want to assign a function to a variable.
Return statements in functions allow you to specify the value that the function will output when it is called. This allows you to use the function's output in other parts of your code. If a function does not have a return statement, its output will be undefined.
To call a function, you simply use the name of the function followed by a set of parentheses. If the function accepts parameters, you would pass them inside the parentheses. The function's code will then be executed, and any return statement will be evaluated.