JavaScript Variables and Data Types Quiz

Variables and Data Types

• In JavaScript, all numbers are represented as floating-point values.
• Variables are declared using the var and let keywords.
• Examples of variable declarations: var age;, var smallNumber;, var initial;, var name;, var isPassed;, var num1, num2, num3;
• Standards for variable names:
  • No spaces
  • No JavaScript reserved keywords
  • Meaningful names
  • Use camel case
• Variable initialization: var age = 20;, var height = 5.5;, var initial = "K";, var name = "Kamal";, var isPassed = true;
• Assigning values to variables: age = 20;, height = 5.5;, initial = "K";, name = "Kamal";, isPassed = true;

Constants

• The const keyword was introduced in ES6 (ES2015) to create constants.
• Example: const x = 5;
• Constants cannot be changed: x = 10; would result in an error.
• Constants must be initialized when declared: const x; would result in an error.

Using Variables

• Reading and using variable values: var age = 20;, document.write(age);, age = 25;, document.write("Modified age = " + age);
• JavaScript is a weakly typed language.

JavaScript Pop-up Boxes

• Alert box: alert("This is an important message !");
• Confirm box: var response = confirm("Press a button");
• Prompt box: var name = prompt("enter your name", "Sir");

Operators

• Arithmetic Operators
• Assignment Operators
• Comparison Operators
• Logical Operators

Control Structures

Selection/Branching

• If-else statements: used to divide the algorithm execution path into branches based on conditions.
• Conditions produce Boolean results.
• Simple if-else example:
  • If the mark is greater than or equals 50, display a message "Pass", else display a message "Fail".
  • Code: if (mark >= 50) { document.write("Pass"); } else { document.write("Fail"); }

Repetition/Iteration/Looping

• While loop
• For loop

Test your knowledge of variable initialization, assignment, and data types in JavaScript with this quiz. Practice understanding the output of different variable and data type operations in JavaScript.