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JavaScript · Unit 8: More on arrays

A refresher: sort takes a comparator (a, b) => a - b. If it gives a negative number, a goes first; if positive, it goes after; if 0, they stay as they were.

And sort sorts the array itself: it doesn't make a copy.

const nums = [30, 5, 12];
nums.sort((a, b) => a - b);
console.log(nums);

Prints

[ 5, 12, 30 ]

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. Multiple choice

    The sort comparator gets a and b and returns a number. If it returns a negative number, what happens?

  3. 3. Predict the output

    What does this code print?

  4. 4. Complete the code

    Complete it to sort from the highest grade to the lowest.

  5. 5. Find the bug

    This program should print the items from cheapest to most expensive. Which line has the error?

  6. 6. Complete the code

    Complete it to sort the cities in alphabetical order.

  7. 7. Predict the output

    This sorts by length and, if there's a tie, in alphabetical order. What does it print?

  8. 8. Put the lines in order

    Order the function that sorts the results of a race: first whoever took the fewest minutes and, if they're tied, whoever is younger.

  9. 9. Multiple choice

    What does this code do?

  10. 10. Predict the output

    The function looks for the highest score. 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.

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