Understanding 'var' in JavaScript: Scope, Hoisting, and Why It Fell Out of Favor

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The 'var' keyword was the original way to declare variables in JavaScript, predating the 2015 introduction of 'let' and 'const'. Unlike modern alternatives, 'var' is function-scoped rather than block-scoped, meaning variables declared inside blocks like 'if' statements remain accessible throughout the entire function. It also allows redeclaration of the same variable without throwing an error, which can lead to unintended bugs. A behavior called hoisting causes 'var' declarations to be moved to the top of their scope before code runs, resulting in 'undefined' rather than an error when a variable is used before its declaration. While most developers today prefer 'let' and 'const' for their stricter scoping rules, understanding 'var' remains useful for reading and maintaining older JavaScript codebases.

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