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A function is a block of statements that can be executed as often as you like. A function can have parameters and can return a value. Functions can be defined in different ways. Perhaps the most common one is the function declaration. It starts with the keyword function. It follows: With the keyword return a value can be returned. At the same time return terminates the function. Statements after a return will not be executed. With
function color() {
  return 'red';
we define a function that returns the value 'red'. The function has no parameters (the parentheses are empty) and contains only the return statement. The function is assigned to the variable color. The function is called by its name:
let result = color();
Now the function is executed. Its return is assigned to the variable result. result therefore has the value 'red'.


Define a function hello that returns 'Hello world!'.
function hello() {
function hello() {
  return 'Hello world!';