Iteration For Loops
An intro to data abstraction
What is for loops
A for loop is a control flow statement that allows you to execute a block of code a certain number of times. It’s particularly useful when you know in advance how many times you want to iterate through a block of code.
Syntax of a for Loop
The syntax of a for loop consists of three main parts:
%%js
for (initialization; condition; increment) {
// Code to be executed on each iteration
}
Initialization: This sets up a counter variable and runs once at the beginning of the loop.
Condition: Before each iteration, the loop checks this condition. If it’s true, the loop continues; if false, the loop ends.
Increment: This updates the counter variable after each iteration.
Example of a for Loop
%%js
for (let i = 1; i <= 5; i++) {
console.log(i);
}
Explanation:
Initialization: let i = 1 sets the counter variable i to 1.
Condition: i <= 5 checks if i is less than or equal to 5.
Increment: i++ increases i by 1 after each iteration.
Output
1
2
3
4
5
Advanced Usage: Looping Through Arrays
You can use a for loop to iterate over elements in an array. Here’s an example:
%%js
let fruits = ["apple", "banana", "cherry"];
for (let i = 0; i < fruits.length; i++) {
console.log(fruits[i]);
}
output
apple
banana
cherry
popcorn 1
Calculate the Sum Write a for loop that calculates the sum of all even numbers from 1 to 20. Output the result to the console.
Hint: Any number divided by two results in a remainder of 1 for odd numbers and 0 for even numbers. The modulo operator (%
) helps you determine this condition. The statement if (n % 2 == 0)
would be true when n
is even.