Video Notes

Looping through arrays

A key technique in programming is making something repeat using loops. A common type of loop is the for loop. Here’s an example looping through an array of items in JavaScript:

let items = ['apple', 'banana', 'cherry', 'date', 'fig'];

for (let item of items) {
    console.log(item);
}

Output:

apple
banana
cherry
date
fig

Numerically looping

In addition to looping through an array, you can define a numerical for that starts at some number and continues until some end point.

for (let i = 0; i < 6; i++) {
    if (i % 2 == 0) {
        console.log(`${i} is an even number`);
    } else {
        console.log(`${i} is an odd number`);
    }
}

Output:

0 is an even number
1 is an odd number
2 is an even number
3 is an odd number
4 is an even number
5 is an odd number

When defining a numerical for loop, you construct the loop using three expressions:

1. Define a “cursor” variable that will iterate through the loop, indicating its start value: let i = 0
2. Define a Boolean expression that once True, will terminate the loop: i < 6
3. Define how the cursor should change each iteration through the loop: i++