JavaScript Fundamentals · Loops · Lesson 11 of 48
Looping Over Arrays
Concept
Looping Over Arrays
A for...of loop lets you iterate directly over the values in an array, without managing an index counter yourself.
This makes the intent of the code clearer — you're saying "for each item in this list" instead of "count from 0 to length, then look up each item by index."
By the end of this lesson
- Explain the core idea behind Looping Over Arrays.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Syntax
for (const item of iterable) {
// code using item
}ExampleRunnable
const fruits = ["apple", "banana", "mango"];
for (const fruit of fruits) {
console.log(fruit);
}Getting the index too, with .forEach()
const fruits = ["apple", "banana", "mango"];
fruits.forEach((fruit, index) => {
console.log(index, fruit);
});Note: forEach() is a method on arrays, and unlike for...of it always gives you the index alongside each value.
for...in for object keys
const student = { name: "Alex", age: 20 };
for (const key in student) {
console.log(key, student[key]);
}Note: for...in loops over an object's keys, while for...of loops over an array's values — mixing the two up is a common source of bugs.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Looping Over Arrays. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Loop over an array of your favorite courses and print each one.
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Console