While Loops in JavaScript (OCR A Level Computer Science): Revision Note

While Loops in JavaScript

• A while loop is a control flow statement that allows a block of code to repeatedly execute as long as a specified condition remains true

• While loops provide a flexible and powerful way to handle situations where the number of iterations is unknown in advance

Syntax of a while loop

The syntax of a while the loop consists of a condition and a code block:

while (condition) {
  // Code to be executed as long as the condition is true
}

• The condition is evaluated before each iteration. If the condition evaluates to true, the code block is executed. If the condition evaluates to false, the loop terminates

Example 1: Counting from 1 to 5

While loop in JavaScript counting from 1 to 5

Example 2: Checking if the password is 'secret'

While loop in JavaScript checking if the password is correct

Do While Loops in JavaScript

• A do while loop is a control flow statement that allows a block of code to repeatedly execute at least once, and then continue execution as long as a specified condition remains true

• Do while loops provide a variation of the while loop with slightly different behaviour

Syntax of a do while loop

The syntax of a do while the loop consists of a code block and a condition:

do {
  // Code to be executed at least once
} while (condition);

• Code Block: The code block is executed first before evaluating the condition

• Condition: The condition is evaluated after executing the code block. If the condition evaluates to true, the loop continues executing. If the condition evaluates to false, the loop terminates

Example: Rolling a die until a desired number is obtained

Do while loop in JavaScript - a dice roll repeats until the target number is met