Summary - Loops

Print a multiplication table using for and while loops.

Summary - Loops

In this group you learned four loop types: for, while, do...while and nested loops. You also learned to exit with break and skip steps with continue.

for (let i = 1; i <= 3; i++) {
  console.log(i);
}

Now let's combine them in one task: a multiplication table with for, and a sum with while. You'll build a real piece of a program using what you've learned.

Exercise A 5x5 multiplication table

Use nested for loops to print a 5x5 multiplication table. The outer loop walks i, the inner loop walks j, both from 1 to 5. In each cell add i * j to a row variable separated by a space, and print each row with console.log(row).

Show example solution

for (let i = 1; i <= 5; i++) {
  let row = "";
  for (let j = 1; j <= 5; j++) {
    row += (i * j) + " ";
  }
  console.log(row);
}

Exercise Sum from 1 to 100

Use a while loop to compute the sum of numbers from 1 to 100. Accumulate it in a total variable. Keep the counter as n, add it to total each step, and increment n. Finally print it with console.log(total).

Show example solution

let total = 0;
let n = 1;
while (n <= 100) {
  total += n;
  n++;
}
console.log(total);

Test yourself

Which loop is best for 10 repeats with a known count?
- for loop
- while loop
- do...while loop
- nested loop
Show answer

for loop — The for loop is ideal for known counts, since init, condition and increment fit on one line.
Match the loop type to its use case

for

loop with known count
while

loop with unknown condition
do...while

run first, then test

Next lesson: Creating and accessing arrays

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