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App Dev Worksheet: Loops over Lists

App development lesson 19: Loops over lists · Set 123 · 40 questions
TalentJR

Developer's tip (One by one): for (let i = 0; i < list.length; i++) visits every item, from position 0. Total: add each item. Count: add 1 when the test is true. Best: keep the biggest so far. The body runs once per item: a list of 5 runs it 5 times.

NameDateTime takenScore ___ / 40
  1. 1.🔁 What number does this code show?
    let marks = [58, 90, 51];
    let count = 0;
    for (let i = 0; i < marks.length; i++) {
      if (marks[i] >= 70) {
        count = count + 1;
      }
    }
    show(count);
  2. 2.🔁 What number does this code show?
    let marks = [12, 15, 4];
    let total = 0;
    for (let i = 0; i < marks.length; i++) {
      total = total + marks[i];
    }
    show(total);
  3. 3.🔁 In for (let i = 0; i < 3; i++), which values does i take? (a) 0, 1, 2, 3 (b) 3 (c) 1, 2, 3 (d) 0, 1, 2
  4. 4.🔁 What does a loop do? (a) repeats code (b) saves photos (c) deletes code (d) draws icons
  5. 5.🔁 What number does this code show?
    let runs = [7, 7, 10, 2, 17];
    let best = 0;
    for (let i = 0; i < runs.length; i++) {
      if (runs[i] > best) {
        best = runs[i];
      }
    }
    show(best);
  6. 6.🔁 A loop over a list of 5 items runs its body how many times? (a) 1 (b) 5 (c) 4 (d) 6
  7. 7.🔁 What number does this code show?
    let runs = [6, 14, 4, 1, 4];
    let total = 0;
    for (let i = 0; i < runs.length; i++) {
      total = total + runs[i];
    }
    show(total);
  8. 8.🔁 What number does this code show?
    let scores = [28, 10, 26];
    let count = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] >= 40) {
        count = count + 1;
      }
    }
    show(count);
  9. 9.🔁 Why use a loop to show 100 messages? (a) it uses more lines (b) it is slower (c) it hides them (d) less code to write
  10. 10.🔁 What number does this code show?
    let steps = [41, 47, 95, 16, 49];
    let count = 0;
    for (let i = 0; i < steps.length; i++) {
      if (steps[i] >= 70) {
        count = count + 1;
      }
    }
    show(count);
  11. 11.🔁 What number does this code show?
    let scores = [4, 18, 15, 12, 18];
    let total = 0;
    for (let i = 0; i < scores.length; i++) {
      total = total + scores[i];
    }
    show(total);
  12. 12.🔁 What is the LAST line this code shows?
    let names = ["Riya", "Aman", "Zoya", "Kabir", "Meera"];
    for (let i = 0; i < names.length; i++) {
      show("Hi, " + names[i]);
    }     (a) Hi, Meera (b) Hi, Zoya (c) Hi, Aman (d) Hi, Riya
  13. 13.🔁 What number does this code show?
    let scores = [12, 13, 2, 18, 16];
    let best = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] > best) {
        best = scores[i];
      }
    }
    show(best);
  14. 14.🔁 What number does this code show?
    let scores = [5, 6, 19];
    let best = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] > best) {
        best = scores[i];
      }
    }
    show(best);
  15. 15.🔁 What number does this code show?
    let steps = [5, 10, 20];
    let best = 0;
    for (let i = 0; i < steps.length; i++) {
      if (steps[i] > best) {
        best = steps[i];
      }
    }
    show(best);
  16. 16.🔁 What number does this code show?
    let scores = [13, 19, 17];
    let total = 0;
    for (let i = 0; i < scores.length; i++) {
      total = total + scores[i];
    }
    show(total);
  17. 17.🔁 What is the LAST line this code shows?
    let names = ["Aman", "Riya", "Meera"];
    for (let i = 0; i < names.length; i++) {
      show("Hi, " + names[i]);
    }     (a) Hi, Riya (b) Hi, Meera (c) Hi, Aman
  18. 18.🔁 What number does this code show?
    let runs = [12, 23, 81];
    let count = 0;
    for (let i = 0; i < runs.length; i++) {
      if (runs[i] >= 40) {
        count = count + 1;
      }
    }
    show(count);
  19. 19.🔁 What is the LAST line this code shows?
    let names = ["Kabir", "Aman", "Riya", "Meera"];
    for (let i = 0; i < names.length; i++) {
      show("Hi, " + names[i]);
    }     (a) Hi, Kabir (b) Hi, Riya (c) Hi, Aman (d) Hi, Meera
  20. 20.🔁 What number does this code show?
    let marks = [17, 7, 6, 10, 15];
    let best = 0;
    for (let i = 0; i < marks.length; i++) {
      if (marks[i] > best) {
        best = marks[i];
      }
    }
    show(best);
  21. 21.🔁 What number does this code show?
    let marks = [4, 1, 12, 13, 3];
    let best = 0;
    for (let i = 0; i < marks.length; i++) {
      if (marks[i] > best) {
        best = marks[i];
      }
    }
    show(best);
  22. 22.🔁 What number does this code show?
    let runs = [9, 10, 4, 9];
    let best = 0;
    for (let i = 0; i < runs.length; i++) {
      if (runs[i] > best) {
        best = runs[i];
      }
    }
    show(best);
  23. 23.🔁 What number does this code show?
    let scores = [20, 10, 17, 9, 2];
    let best = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] > best) {
        best = scores[i];
      }
    }
    show(best);
  24. 24.🔁 What is the LAST line this code shows?
    let names = ["Riya", "Zoya", "Kabir", "Aman"];
    for (let i = 0; i < names.length; i++) {
      show("Hi, " + names[i]);
    }     (a) Hi, Aman (b) Hi, Zoya (c) Hi, Kabir (d) Hi, Riya
  25. 25.🔁 What number does this code show?
    let runs = [20, 2, 14, 10];
    let total = 0;
    for (let i = 0; i < runs.length; i++) {
      total = total + runs[i];
    }
    show(total);
  26. 26.🔁 What is the LAST line this code shows?
    let names = ["Riya", "Zoya", "Aman"];
    for (let i = 0; i < names.length; i++) {
      show("Hi, " + names[i]);
    }     (a) Hi, Zoya (b) Hi, Riya (c) Hi, Aman
  27. 27.🔁 What number does this code show?
    let scores = [10, 8, 1, 3];
    let best = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] > best) {
        best = scores[i];
      }
    }
    show(best);
  28. 28.🔁 What number does this code show?
    let steps = [16, 17, 18];
    let total = 0;
    for (let i = 0; i < steps.length; i++) {
      total = total + steps[i];
    }
    show(total);
  29. 29.🔁 What number does this code show?
    let scores = [70, 33, 26, 76];
    let count = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] >= 40) {
        count = count + 1;
      }
    }
    show(count);
  30. 30.🔁 What number does this code show?
    let scores = [17, 11, 10, 10];
    let total = 0;
    for (let i = 0; i < scores.length; i++) {
      total = total + scores[i];
    }
    show(total);
  31. 31.🔁 What number does this code show?
    let scores = [7, 2, 4, 14];
    let total = 0;
    for (let i = 0; i < scores.length; i++) {
      total = total + scores[i];
    }
    show(total);
  32. 32.🔁 What number does this code show?
    let runs = [36, 73, 82];
    let count = 0;
    for (let i = 0; i < runs.length; i++) {
      if (runs[i] >= 60) {
        count = count + 1;
      }
    }
    show(count);
  33. 33.🔁 What is the LAST line this code shows?
    let names = ["Riya", "Aman", "Arjun", "Meera", "Zoya"];
    for (let i = 0; i < names.length; i++) {
      show("Hi, " + names[i]);
    }     (a) Hi, Arjun (b) Hi, Zoya (c) Hi, Riya (d) Hi, Aman
  34. 34.🔁 What number does this code show?
    let steps = [9, 6, 20, 7];
    let best = 0;
    for (let i = 0; i < steps.length; i++) {
      if (steps[i] > best) {
        best = steps[i];
      }
    }
    show(best);
  35. 35.🔁 What number does this code show?
    let runs = [3, 2, 2];
    let total = 0;
    for (let i = 0; i < runs.length; i++) {
      total = total + runs[i];
    }
    show(total);
  36. 36.🔁 What number does this code show?
    let scores = [35, 60, 78, 47];
    let count = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] >= 60) {
        count = count + 1;
      }
    }
    show(count);
  37. 37.🔁 What number does this code show?
    let scores = [92, 78, 21];
    let count = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] >= 60) {
        count = count + 1;
      }
    }
    show(count);
  38. 38.🔁 What number does this code show?
    let scores = [18, 15, 3];
    let best = 0;
    for (let i = 0; i < scores.length; i++) {
      if (scores[i] > best) {
        best = scores[i];
      }
    }
    show(best);
  39. 39.🔁 What number does this code show?
    let marks = [42, 65, 79, 40];
    let count = 0;
    for (let i = 0; i < marks.length; i++) {
      if (marks[i] >= 50) {
        count = count + 1;
      }
    }
    show(count);
  40. 40.🔁 list.length tells you ___. (a) the first item (b) the last item (c) how many items it has (d) the biggest item

Answer key

  1. 1
  2. 31
  3. 0, 1, 2
  4. repeats code
  5. 17
  6. 5
  7. 29
  8. 0
  9. less code to write
  10. 1
  11. 67
  12. Hi, Meera
  13. 18
  14. 19
  15. 20
  16. 49
  17. Hi, Meera
  18. 1
  19. Hi, Meera
  20. 17
  21. 13
  22. 10
  23. 20
  24. Hi, Aman
  25. 46
  26. Hi, Aman
  27. 10
  28. 51
  29. 2
  30. 48
  31. 27
  32. 2
  33. Hi, Zoya
  34. 20
  35. 7
  36. 2
  37. 2
  38. 18
  39. 2
  40. how many items it has

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