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66Declaring Variables with var
67Declaring Variables with let
68Declaring Variables with const
69Variable Naming Rules
70Variable Initialization
71Multiple Declarations in One Statement
72Const and Object Mutability
73Const and Array Mutability
74When to Use let vs const
75Undeclared Variables and Implicit Globals
76Var vs Let vs Const Summary
77What is Scope?
78Global Scope
79Function Scope
80Block Scope Basics
81Blocks vs Functions
82Lexical Scope
83Nested Scopes
84Scope Chain Lookup
85Shadowing Variables
86Loop Scope with let
87Loop Scope with var
88Scope and Closures Preview
89Best Practices for Scope
90What is Hoisting?
91Var Hoisting: Declaration vs Initialization
92Function Declaration Hoisting
93Let and Const: The Temporal Dead Zone (TDZ)
94TDZ Timeline and Duration
95Common TDZ Pitfalls
96Function Expressions vs Declarations
97Class Hoisting and the TDZ
98Import Hoisting Behavior
99Best Practices: Declare Before Use

66Declaring Variables with var
67Declaring Variables with let
68Declaring Variables with const
69Variable Naming Rules
70Variable Initialization
71Multiple Declarations in One Statement
72Const and Object Mutability
73Const and Array Mutability
74When to Use let vs const
75Undeclared Variables and Implicit Globals
76Var vs Let vs Const Summary
77What is Scope?
78Global Scope
79Function Scope
80Block Scope Basics
81Blocks vs Functions
82Lexical Scope
83Nested Scopes
84Scope Chain Lookup
85Shadowing Variables
86Loop Scope with let
87Loop Scope with var
88Scope and Closures Preview
89Best Practices for Scope
90What is Hoisting?
91Var Hoisting: Declaration vs Initialization
92Function Declaration Hoisting
93Let and Const: The Temporal Dead Zone (TDZ)
94TDZ Timeline and Duration
95Common TDZ Pitfalls
96Function Expressions vs Declarations
97Class Hoisting and the TDZ
98Import Hoisting Behavior
99Best Practices: Declare Before Use

Lesson 75 of 2,723·3. Variables and ScopePro lesson

Undeclared Variables and Implicit Globals

Discover the dangers of assigning to undeclared variables and how strict mode prevents it.

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