1. Dynamic Typing, Scope & ES6+ Syntax

### Learning Objectives - Differentiate between block-scoped `let`/`const` and legacy function-scoped `var`. - Understand JavaScript dynamic type coercion vs strict equality comparison (`==` vs `===`). - Use template literals and arrow function syntax concisely. - Unpack objects and arrays cleanly using destructuring assignment and spread (`...`) operators. --- ### Lexical Scope & Variable Hoisting In ECMAScript 6 (ES6), `let` and `const` were introduced to enforce **Block Scope**, placing declared variables inside a Temporal Dead Zone (TDZ) prior to execution. This eliminates variable hoisting bugs historically caused by function-scoped `var`.

### Key Terminology - **Temporal Dead Zone (TDZ)**: Time window between scope entry and variable initialization where accessing `let`/`const` throws a `ReferenceError`. - **Strict Equality (`===`)**: Checks both value and type equality without implicit type coercion. - **Spread Operator (`...`)**: Unpacks iterable collections into individual arguments or elements. --- ### Common Pitfalls 1. **Implicit Type Coercion**: Using `==` converts string `"5"` to number `5` implicitly (`"5" == 5` is true, but `"5" === 5` is false). 2. **Mutating `const` Reference Objects**: Declaring an object with `const` prevents reassignment of the variable reference, but DOES NOT freeze object property mutations.