What is the difference between var, let, and const in JavaScript? When would you use each one?
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In JavaScript, var, let, and const are used to declare variables, but they differ in terms of scope and mutability.
If a variable is declared with var outside of a function, it becomes a global variable and is accessible throughout the entire script
let or const are only accessible within the block in which they are declared. Variables declared with let can be updated within their scope, but cannot be re-declared. Variables declared with const.
Use var if you need to declare a variable that is accessible within a function or throughout the entire script and you need to update or re-declare it within its scope.
Use let if you need to declare a variable that is only accessible within a block and you need to update it within its scope.
Use const if you need to declare a variable that is only accessible within a block and its value will not change after it is initialized.