Turning def Into function

Turning def Into function

In this lesson, you ported the crew’s describe_dock() function to JavaScript, then added the free slots to it and saw what happens to a call that wasn’t updated.

• Where Python writes def, JavaScript writes a function declaration, one way to write a named function: the keyword function, the name in camelCase, and the parameters in parentheses, as in Python.
• Braces mark the body, because JavaScript doesn’t read indentation, as with if and loops.
• return hands the value back, as in Python.
• JavaScript doesn’t require a call to pass every argument. A parameter with no argument starts out as undefined, and a template literal turns it into the text undefined. Where Python stops with a TypeError when it reaches the call, JavaScript runs and prints a wrong line.
• A function that ends without a return gives back undefined, where Python gives None.
• JavaScript doesn’t stop at the call the way Python does, so when you change a function’s parameters, update every call, then run the file and read the output. An undefined in a line means a value that was never passed, or a return that’s missing.
• Python lets you give a parameter a default, and JavaScript can too. Defaults and keyword arguments come later.

Here’s the port with the free slots added, where the Elm Street call wasn’t updated:

function describeDock(name, bikes, slots) {
  return `${name}: ${bikes} bikes, ${slots} free`;
}

console.log(describeDock("Elm Street", 0));
console.log(describeDock("Harbor Square", 14, 1));
console.log(describeDock("Station Road", 6, 8));
console.log(describeDock("Market Hall", 0, 10));
console.log(describeDock("Riverside Park", 11, 2));