Variables and Data Types

Continue your JavaScript Tutorial learning path with hands-on explanation, code practice, and quiz.

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Course

JavaScript Tutorial

Estimated Time

8 min

Progress

Track Position

2 / 73

Lesson Overview

Simple Explanation

var function scope rakhta hai, let block scope rakhta hai aur const reassign nahi hota. Common data types: string, number, boolean, null, undefined, symbol, bigint.

Code Explanation

Har variable different type hold kar raha hai. typeof operator se runtime type check hota hai.

Output Description

Console me values aur unke types show honge.

Practice Exercise

Har type ka ek variable banao aur console.table me display karo.

Extra Explanation

Why This Matters

Variables and Data Types is core to dynamic behavior. Strong fundamentals here help you build forms, API flows, and interactive UI with confidence.

Real-World Workflow

Complex features are usually split into small functions, then verified through focused logging and tiny test cases.

Common Mistakes to Avoid

Avoid uncontrolled globals, weak error handling, and ignored async states. Define clear input-output expectations for each function.

Example + Live Practice

<script>
  var city = "Karachi";
  let age = 22;
  const isActive = true;
  let emptyValue = null;
  let notAssigned;
  const id = Symbol("id");
  const huge = 9007199254740993n;

  console.log(typeof city, typeof age, typeof isActive);
  console.log(emptyValue, notAssigned);
  console.log(typeof id, typeof huge);
</script>

Try It Yourself

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