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Anonymous Functions

Anonymous functions are true to form in that they have no name. They're useful when defining a function that will only be used once or to create a quick closure.

Let's say we have a function conversions that accepts another function, converter as input:

function conversions(converter, x, y, z) {
  const convertedX = converter(x);
  const convertedY = converter(y);
  const convertedZ = converter(z);
  console.log(convertedX, convertedY, convertedZ);
}

We could define a function normally and then pass it in by name... but if we only want to use it in this one place, we can define it inline as an anonymous function:

// using a named function
function double(a) {
  return a + a;
}
conversions(double, 1, 2, 3);
// 2 4 6

// using an anonymous function
conversions(
  function (a) {
    return a + a;
  },
  1,
  2,
  3,
);
// 2 4 6

Assignment

Complete the printReports function. It takes a sequence of messages, intro, body, and outro. It should call printCostReport once for each message, in order.

For each call to printCostReport, you should pass:

an anonymous function that calculates the cost of a message as an integer
the message itself

The cost for each type of message is calculated like this:

Intro: 2x the message length
Body: 3x the message length
Outro: 4x the message length

Use the built-in length property to get the length of a string:

const helloLen = "hello".length;
// helloLen = 5