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JavaScript·Advanced·Coding·1 min read

How is currying implemented with closures?

Short interview answer

Each returned function closes over arguments received at an earlier stage. The final function combines all captured values to produce the result. A generic curry utility also tracks arity and accumulates arguments across calls.

Example

JavaScript
function curry(fn) {  return function curried(...args) {    return args.length >= fn.length      ? fn(...args)      : (...more) => curried(...args, ...more); // closes over `args`  };}
const sum3 = curry((a, b, c) => a + b + c);sum3(1)(2)(3);   // 6sum3(1, 2)(3);   // 6

Key takeaway

Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.

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