var, let, and const in JavaScript: Key Differences Every Developer Should Know

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JavaScript offers three variable declaration keywords — var, let, and const — each with distinct scoping and hoisting behaviors introduced or clarified in ES6. The var keyword is function-scoped and allows redeclaration, meaning the same variable name can be declared multiple times without error. In contrast, let is block-scoped and prevents redeclaration, reducing bugs caused by accidental variable overwrites. A key behavioral difference involves hoisting: var declarations are hoisted and initialized as undefined, while let and const are placed in a Temporal Dead Zone, throwing a ReferenceError if accessed before their declaration. These distinctions make let and const safer and more predictable choices for modern JavaScript development.

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