What is a Function?

Functions allow you group together some code, give this code a name, and reuse it later, addressing it by name. Let's see an example:

function sum(a, b) {
    var c = a + b;
    return c;
}

What are the parts that make up a function?

• The function statement.

• The name of the function, in this case sum.

• Expected parameters (arguments), in this case a and b. A function can accept zero or more arguments, separated by commas.

• A code block, also called the body of the function.

• The return statement. A function always returns a value. If it doesn't return value explicitly, it implicitly returns the value undefined.

Note that a function can only return a single value. If you need to return more values, then simply return an array that contains all of the values as elements of this array.

Calling a Function

In order to make use of a function, you need to call it. You call a function simply by using its name followed by any parameters in parentheses. "To invoke" a function is another...