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Recursion with text

JavaScript · Unit 11: Recursion

Strings work just like arrays: the first letter is t[0] and the rest is t.slice(1), a string with one letter fewer. The base case is usually the empty string, "".

const t = "sun";
console.log(t[0]);
console.log(t.slice(1));

Prints

s
un

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. Predict the output

    This function counts the vowels. What does it print?

  3. 3. Complete the code

    Fill in the blank so it prints "rats".

  4. 4. Find the case that fails

    flip(t) should return the string backwards. With the empty string it should return an empty string. Which call breaks it?

  5. 5. Predict the output

    Now each call prints the string it gets. What does it print?

  6. 6. Find the bug

    This program should print true, because "wow" is a palindrome. Which line has the error?

  7. 7. Complete the code

    Fill in the comparison so it prints true.

  8. 8. Multiple choice

    palindrome("Anna") gives false, with this lesson's function. Why?

  9. 9. Put the lines in order

    To check phrases you need to remove their spaces. Put noSpaces in order: it returns the string without them.

  10. 10. Predict the output

    A whole phrase. 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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