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How do you convert a callback-based function to a Promise?

Q: How do you convert a callback-based function to a Promise?

**Core concept (TL;DR).** Wrap the callback API in a new Promise : call the original function inside the executor, and translate its callback into resolve / reject . For Node's (err, data) convention, reject on err and resolve with data . This is exactly what util.promisify automates. Bridge a callback API to a Promise ca

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JSPromisify a Node-style callback

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