For loop in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a for loop used for in JavaScript?

A for loop is used to repeat a block of code a specific number of times. It helps automate repetitive tasks.

beginner

Identify the three main parts inside the parentheses of a for loop: for (___; ___; ___)

The three parts are: 1) Initialization (sets a starting point), 2) Condition (checks if the loop should continue), 3) Update (changes the loop variable each time).

beginner

What will this loop print?<br><pre>for (let i = 0; i &lt; 3; i++) { console.log(i); }</pre>

It will print:<br>0<br>1<br>2<br>Because it starts at 0 and runs while i is less than 3, increasing i by 1 each time.

intermediate

How can you stop a for loop early?

You can use the break statement inside the loop to stop it immediately when a condition is met.

intermediate

What happens if the condition in a for loop is always true?

The loop will run forever, causing an infinite loop, which can freeze or crash your program.

Which part of the for loop controls how many times the loop runs?

A The loop body

B The initialization

C The condition

D The update

The condition is checked before each loop run to decide if the loop should continue.

What does this loop do?<br>

for (let i = 5; i > 0; i--) { console.log(i); }

A Counts up from 5 to 0

B Counts up from 0 to 5

C Counts down from 0 to 5

D Counts down from 5 to 1

It starts at 5 and decreases i by 1 each time until i is no longer greater than 0.

What keyword stops a for loop immediately?

A break

B stop

C continue

D exit

break exits the loop immediately.

What will happen if you forget to update the loop variable in a for loop?

A The loop will run once

B The loop will run infinitely

C The loop will not run

D The loop will run twice

Without updating, the condition may never become false, causing an infinite loop.

Which of these is a valid for loop header?

A for (let i = 0; i < 5; i++)

B for (i < 5; i++)

C for i = 0; i < 5; i++

D for (let i = 0; i++)

Option A has the correct syntax with initialization, condition, and update inside parentheses.

Explain the three parts of a for loop and how they work together.

Think about how the loop starts, checks if it should continue, and changes each time.

Describe a real-life situation where a for loop could help automate a task.

Imagine doing something many times, like counting items or sending messages.