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Chapter 2: Variables and the Modern Type System

Learn how to manage data in 2026 using let, const, and the modern type system including BigInt and Symbols.

JavaScriptFundamentals

Variables and the Modern Type System

Understanding how JavaScript handles data is fundamental. We’ll look at the modern way to declare variables and the complete list of data types available in 2026.

Key Topics

  • Why var is history
  • let vs const: Best practices
  • Primitive Types: String, Number, Boolean, BigInt, Symbol, null, undefined
  • Dynamic typing vs. Type inference awareness