warmup8 min

Implement once(fn)

Implement `once(fn)`

Write once(fn) that returns a wrapped version of fn which only ever actually calls fn on the first invocation — every subsequent call returns the same cached result without calling fn again.

const init = once(() => { console.log("initializing"); return "ready"; });
init(); // logs "initializing", returns "ready"
init(); // no log, still returns "ready"

Your code

Results

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Stuck? This challenge exercises:

javascript.closures