meet it

A loop visits every item in an array.

A for...of loop walks along an array, one item at a time. for (const coin of coins) reads like plain English: for each coin of the coins, run the block.

Each lap, coin is a fresh box holding the next item. It can be a const, because nothing changes it inside the block. There is no counter to manage and no index to get wrong.

To add things up, keep a . Start a box at 0 before the loop, add each item to it inside, and show it after the loop ends.

let coins: number[] = [2, 5, 1, 2];
let total: number = 0;
for (const coin of coins) {
  total = total + coin;
}
console.log("Piggy bank:", total);

Name the lap box after one item, like coin for coins, so the loop reads clearly.

guess first

Three friends arrive. What will this show?

Guess before you run it. Wrong guesses are how you learn, and nothing is marked.

let friends: string[] = ["Mo", "Ana", "Kit"];
for (const friend of friends) {
  console.log(`Hi ${friend}!`);
}

your turn

Your turn. Add up your shopping.

Type three prices, as numbers, into the array. Guess the total, then press run to check.

Your code

press run to see what happens

fix it

Three good scores, but a tiny total. Fix it!

Broken code to fix

press run to see what happens

The total comes out as 4, the last score. What happens to the total on each lap?
total = score throws away the old total and keeps only this score. You want to add to it.
Change line 4 to total = total + score; then press run.

nailed it

you can add up a whole array. :D

for...of visits every item of an array in order.
Start a running total at 0, before the loop.
Add each item to the total inside the loop.

new words in your collection

for...of
running total

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A for...of loop visits every item in an array.

Three friends arrive. What will this show?

Your turn. Add up your shopping.

Three good scores, but a tiny total. Fix it!

you can add up a whole array. :D

A loop visits every item in an array.