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