Guide to High School Computer Science
  • 💻Introduction
    • windows & Python Development
    • macOS & Python Development
    • Visual Studio Code Settings
    • Set up Github
    • Author Page
  • 🧠Prerequisite Skills
    • Keyboard Typing
    • Files & Directories
    • Use of Command Line
    • Git & GitHub
    • Markdown
    • Starting Your Python Project
  • 🐍Python Programming
    • 🍎Python Basics
      • What is Python?
      • Procedural Programming & Programming Paradigms
      • String Formatting
      • Data Types
      • Input & Output to Console
      • Working with Numbers
      • Useful Built-in Functions
      • Math & Random Module
      • Boolean Data Object
      • Comparison, Logical, and Membership Operators
      • If Statements
      • Binary Decisions
      • Multiple Decisions
      • Nested Conditions
      • [EXTRA] Bitwise Operators
      • [EXTRA] Python Style Guide
    • ⏮️Iterations
      • Introduction to While Loops
      • Infinite Loop
      • Controlling Your While Loops
      • Introduction to For Loops
      • For Loops w/ Numeric Sequences
      • For Loops w/ Strings & Lists
      • Iterable Functions w/ For Loops
    • 📦Collections
      • Strings
        • String Basics
        • String Indexing
        • String Slicing
        • String Operators & Functions
        • Basic String Methods
        • String Methods Extended
        • String Methods Document
      • Tuples & Lists
        • Tuples
        • List Basics
        • List are Mutable
        • Adding Items to a List
        • Removing Items from a List
        • Search & Reverse a List
        • List Comprehension
        • List Methods Document
      • Sets
      • Dictionary
      • How to Store Multiple Data Items
    • 💡Defining Functions
      • Functions
      • print() vs return
      • Pre-determined Arguments
      • Nested Functions
      • Map & Filter
      • [Extra] Dynamic Arguments
    • 💾File I/O
      • How to Save Text to an External File
      • Reading CSV in Python
      • Reading JSON in Python
    • 🔨Basic Python Projects
      • Basic Calculator
        • Improving the calculator
        • Exercise Set 1
        • Exercise Set 2
        • 💎Streamlit Application #1
      • Basic Password Generator
        • Exercise Set 3
        • Exercises Related to Math
        • 💎Streamlit Application #2
      • A To-Do Task List
    • ⏳Introduction to Algorithmic Thinking
      • Big-O Notation
      • Basic Algorithms
        • Linear Search
        • Binary Search
        • Basic Sorting Algorithms
      • Recursion
      • Brute Force Algorithms
      • Greedy Algorithm
        • Time on Task (CCC 2013 J4)
        • Dijkstra’s Algorithm
      • Divide and Conquer
        • Merge Sort
      • Dynamic Programming
    • 🤯Object Oriented Programming
      • Class & Objects (Definitions)
      • OOP in Python
      • Encapsulation
      • Polymorphism
      • Inheritance & Overriding
      • Override Magic Methods
      • Case Study: 2D Vectors
      • Case Study: Deck of Cards
      • Exercise
      • Abstract Data Types
      • Case Study: Static 1D Array From Java
    • Competitive Programming
      • Is This Sum Possible?
        • Is the dataset sorted?
        • Searching for a value
        • Determine if the difference between an integer from the array and the target value exists
        • Sorting Algorithms
        • Using Two Pointers
      • Two Sum - LeetCode
        • Generate all possible pairs of values
        • Subtract each value from the target, see if the difference exists in the list
      • Longest Common Prefix - LeetCode
        • Compare all possible prefixes
        • Create the longest common prefix with the direct neighbour
      • Length of Last Word - LeetCode
        • Compare all possible prefixes
      • Where can I go from one point to another?
      • Sample Outline
    • IB Recipe Book
  • 💾Python & Databases
    • Intro to Databases & Data Modeling
      • Common Data Types in SQL
      • Introduction to ERDs
      • Primary Keys and Foreign Keys
      • Database Normalization
    • What is SQL?
      • Getting Started
      • SELECT Queries
        • Selection with Conditions
        • Selection with Fuzziness
        • Selection and Sorting in Order
        • Selection without Duplicates
        • Selection with Limited Number of Outputs
      • AGGREGATE Queries
        • Counting Rows
        • Sum, Average, Min/Max Queries
        • Working with Aggregate Queries
        • Power of using Groups
        • Exercise
      • Interacting with Multiple Table
      • Inserting Data
      • External Resource
  • ☕Java Essentials
    • Basics
      • Starting Java
      • Data & Variables
      • Handling User Inputs & Type Conversion
      • Arithmetic
      • IPO Model
      • Basic Built-in Methods
      • Exercise Questions
    • Conditionals
      • Boolean Operators
      • Compare Strings
      • If Statements
      • If Else Statements
      • Making Multiple Decisions
      • Using Switch
      • Flowchart Symbols
      • Exercise Questions
    • Iterations
      • While Loops
      • For Loop
      • Exercises
    • Java Type Casting
    • Strings
      • Common String Practices
      • String Formatting
      • Java Special Characters
    • Collection
      • Arrays
      • For Each Loop
      • ArrayList
      • Exercise Questions
    • Static Methods
      • (Aside) Clearing your Console
    • Randomness in Java
    • Delayed Output in Java
    • Java Output Formatting
    • Java Style Guide
  • 🛠️JavaScript Programming
    • Our Programming Editor & Workflow
      • Hello, world!
      • Commenting & Variables
      • Data in JavaScript
      • Operators
      • String Formatting
      • Getting User Input
    • JavaScript Exercise Set 1
    • Making Decisions
      • Comparing Values
      • Combining Boolean Comparisons
      • Creating Branches
    • JavaScript Exercise Set 2
    • While Loops
      • Infinite While Loop
      • While Loops and Numbers
      • While Loops and Flags
      • While loops w/ Strings
    • JavaScript Exercise Set 3
    • Subprograms & Functions
      • Creating a Function in JavaScript
      • Function with Input and Assignable Output
    • JavaScript Exercise Set 4
  • 💾Topics in CS
    • Computer Environments & Systems
      • Computer Components
        • In-depth Explanations
      • File Maintenance
      • Computer & Safety
      • Software Development
      • Bits & Binary
    • Careers related to Computer Science
    • Postsecondary Opportunities
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  1. JavaScript Programming
  2. While Loops

While Loops and Flags

When writing programs that don't necessarily deal with numbers, you may use a flag based loop to help you do repetitions.

There are some problems that the end point of the task is unclear. In such scenario, it is helpful to write a potential infinite loop and construct an exit mechanism to get out of it.

Example of a flag

Please note that it does not need to be called a flag, but it is a representation of a flag being either being true or false.

let flag = true;

while (flag) {
    console.log("Hello!");
    
    let end = prompt("Do you want to end the loop? (Yes/No): ");
    
    if (end == "Yes") {
        flag = false;
        console.log("good bye!");
    }
}
  1. Initialization: You start by setting a variable called flag to true.

  2. Condition Check: You have a loop that will continue to run as long as flag is true.

  3. Loop Execution: Inside the loop, three main actions occur:

    • The message “Hello!” is printed to the console.

    • The program prompts the user with the question “Do you want to end the loop? (Yes/No):” and waits for the user’s input.

    • If the user types “Yes”, the flag variable is set to false, and the message “good bye!” is printed to the console.

  4. Repetition: After each iteration, the loop checks the condition again. If flag is still true, the loop repeats the actions. This process continues until the user types “Yes” (case sensitive).

  5. Termination: When the user types “Yes”, the condition flag becomes false, so the loop stops running, and the program prints “good bye!”.

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Last updated 5 months ago

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