Repeating with for Loops

Imagine you want to print the numbers 1 to 5. You could write five console.log lines, but that gets tedious fast. A loop repeats code for you.

The most common is the for loop. It looks busy at first, but it has just three parts separated by semicolons.

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

The three parts inside the brackets are:

1. let i = 1 the start: create a counter called i beginning at 1.
2. i <= 5 the condition: keep looping while this is true.
3. i++ the step: add 1 to i after each loop. (i++ is shorthand for i = i + 1.)

So this loop runs with i equal to 1, then 2, 3, 4, 5, printing each one, then stops because 6 <= 5 is false.

Looping over an array

Loops and arrays are best friends. Use the counter as the index to visit every item:

let fruits = ["apple", "banana", "cherry"];

for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}

Here we start at 0 (the first index) and continue while i is less than the array's length.

Try it yourself

Run the loop, then try changing the numbers or adding items to the array.