Summary

In this lesson, you learned that:

• A loop repeats a block of code. Each run of the block is an iteration.
• while (condition) { ... } repeats the block while the condition is true. Something in the loop must change so that the condition becomes false at some point. Otherwise, the loop never ends, and in these exercises, the program is stopped after 5 seconds.
• i++ and i-- add or subtract 1, total += price adds to a variable and total -= price subtracts from it.
• for (let i = 0; i < 5; i++) { ... } has the start, the condition and the step on one line. The counter must be a let, because the step changes it.
• A classic for goes through the indexes of an array with i < list.length (not <=).
• for (const item of list) { ... } goes through the elements of an array, or the characters of a text, one by one.
• Typical patterns: the sum (a variable that starts at 0 before the loop and adds each value with +=), the average (the sum divided by .length), counting (count++ inside an if) and the largest value (start with the first element and keep every larger one).
• break ends the whole loop, for example when you have found what you were looking for.
• continue skips the rest of the current iteration and goes on to the next one.
• Loops can be nested: the inner loop runs all the way through in every iteration of the outer one.

Next comes another small project: a game of hangman. Then, in the lesson on functions, you will learn to give a piece of code a name and run it whenever you need it, for example a function that adds up any array of numbers.