Loops - JS Basics in My Style

Present State

Loops in JavaScript provide a way to execute a block of code multiple times. Depending on the loop type and condition, the code will repeat until the condition evaluates to false. Common loop types include for, while, and do-while, each with their own specific use-cases.

Code Example

This example demonstrates the use of different loop types in JavaScript:

JavaScript Loops Example


// For loop
for (let i = 1; i <= 5; i++) {
  console.log("For loop count:", i);
}

// While loop
let j = 1;
while (j <= 5) {
  console.log("While loop count:", j);
  j++;
}

// Do-while loop
let k = 1;
do {
  console.log("Do-while loop count:", k);
  k++;
} while (k <= 5);

This code demonstrates:

Using a for loop for a known number of iterations.
Using a while loop for condition-based repetition.
Using a do-while loop to ensure the block executes at least once.

Description

JavaScript loops are used to execute the same block of code multiple times:

for loop: Best when the number of iterations is known. Syntax: for (init; condition; increment).
while loop: Used when the condition is checked before each iteration.
do-while loop: Executes the block at least once, then repeats as long as the condition is true.

Loops help reduce repetitive code and increase efficiency in operations like traversing arrays, performing calculations, and handling user input.

Applications

Traversing Arrays: Loop through array elements for processing or display.
Input Validation: Continuously prompt the user until valid input is received.
Animation Loops: Create animations that update frame-by-frame.
Batch Operations: Automate repetitive calculations or operations.

Multiple Choice Questions

Q1: What is the minimum number of times a do-while loop will execute?

A. 0
B. 1
C. Infinite
D. Depends on the condition

Answer: B. 1

Q2: Which loop is ideal when the number of iterations is known beforehand?

A. while
B. do-while
C. for
D. infinite

Answer: C. for

Q3: What happens if the loop condition never becomes false in a while loop?

A. It runs once and stops
B. It results in an infinite loop
C. It throws an error
D. It exits automatically

Answer: B. It results in an infinite loop

Q4: Where is the loop condition evaluated in a do-while loop?

A. Before the loop body
B. After the loop body
C. Inside the loop body
D. Only once

Answer: B. After the loop body