Arrays and tuples

An array holds any number of values of one type. A tuple is a fixed-length array where every position has its own type.

Key points

Two ways to write the same type: number[] and Array<number>.
A string cannot go into a number array: push("ten") is flagged as an error.
The tuple [string, number] has exactly two items: a string, then a number.
A tuple is easy to unpack into variables: const [name, age] = entry.

Example

const scores: number[] = [7, 9, 10];const tags: Array<string> = ["ts", "web"];scores.push(8);// scores.push("ten"); // error: string is not assignable to number const point: [number, number] = [3, 4];const entry: [string, number] = ["Anna", 25];const [who, age] = entry; console.log(`Scores: ${scores.join(", ")}; tags: ${tags.length}`);console.log(`${who} is ${age}, point x = ${point[0]}`);

scores.push(8) works, push("ten") does not. The tuple entry is unpacked into two variables, and each keeps the right type: who is a string, age is a number.

Task

How to use the editor⌘ Enter or Ctrl Enter runs the code, ⇧ ⌘ Enter checks the task.Tab and Shift Tab indent the line or the selection; Esc, then Tab leaves the editor.The check compares what the program printed with the task; spaces at line ends do not matter.After two failed checks you may open the solution. Your code is kept in this browser.

Type the cart as [string, number][], loop over it with for...of, print every item as "Coffee: 4" and finish with "Total: 12".

// TODO: give cart the type [string, number][]// (an array of tuples: item name and price)const cart = [  ["Coffee", 4],  ["Croissant", 3],  ["Juice", 5],]; let total = 0;// TODO: loop over cart, print every item as "Coffee: 4"// and add its price to total console.log(`Total: ${total}`);

// TODO: give cart the type [string, number][]
// (an array of tuples: item name and price)
const cart = [
  ["Coffee", 4],
  ["Croissant", 3],
  ["Juice", 5],
];

let total = 0;
// TODO: loop over cart, print every item as "Coffee: 4"
// and add its price to total

console.log(`Total: ${total}`);

Output

What your program prints appears here.