What are the three main types of scope in JavaScript?
Global scope (variables accessible everywhere), function scope (variables accessible only inside a function), and block scope (variables accessible only inside a pair of braces).
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More FAQs in Global, Function, and Block Scope in JavaScript
var is function-scoped and leaks out of blocks; in the global scope it becomes a property of window. let and const are block-scoped and stay inside blocks; in the global scope they live in a separate global lexical environment.
Yes. var ignores block boundaries (except function bodies), so a var inside an if is hoisted to the enclosing function or global scope. let and const are block-scoped and do not leak.
No. In ES modules, top-level let, const, and var are module-scoped, not global. They are only accessible outside the module if explicitly exported. This prevents global pollution.
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