JavaScript Variable Scope Explained: Global, Function, and Block Levels

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In JavaScript, a variable's scope determines where it can be accessed within a program. Global variables are declared outside any function or block and are accessible throughout the entire codebase. Function-scoped variables exist only within the function they are declared in, while block-scoped variables using let or const are confined to the curly-brace block they appear in. The older var keyword is function-scoped and not block-scoped, unlike the modern let and const. JavaScript also supports hoisting for var and function declarations, but not for let and const.

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ProgrammingHacker News ·

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