Skip to the content
Start

reduce and sorting

JavaScript · Unit 5: Arrays

reduce boils the whole array down to a single value. It takes two things: an arrow with the accumulator and the item, and the value the accumulator starts at.

const nums = [10, 20, 30];
const total = nums.reduce(
  (sum, n) => sum + n,
  0
);
console.log(total);

Prints

60

The rest of the explanation is in the lesson, which is part of the full plan.

Exercises in this lesson

You do them in the app, which checks them on the spot and explains why.

  1. 1. Predict the output

    What does this code print?

  2. 2. Complete the code

    Complete it so the result is 24, the product of the three.

  3. 3. Multiple choice

    What does this code do?

  4. 4. Predict the output

    What does this code print?

  5. 5. Complete the code

    Complete it to sort the points from highest to lowest.

  6. 6. Find the bug

    This program should print the points from lowest to highest. Which line has the error?

  7. 7. Predict the output

    What does this code print?

  8. 8. Predict the output

    What does this code print?

  9. 9. Put the lines in order

    Put in order the function that adds up the prices with reduce.

  10. 10. Predict the output

    These are the points of four players. What does it print?

Do this lesson

It opens in your browser. This lesson is part of the full plan; the first unit of each course is free.

See all lessons →