Instruction: Define a closure and provide a simple use case where it might be utilized.
Context: This question probes the candidate's understanding of closures, a powerful feature of JavaScript that enables data encapsulation and private methods.
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For example, let's consider a simple use case where closures can be particularly useful: creating a function that generates unique IDs for users. In a typical application, you might want to assign a unique ID to each user without having to expose the internal counter or mechanism you're using to generate these IDs. This is where closures come into play.
function createIdGenerator() { let id = 0; return function() { ++id; return `user_${id}`; }; }...