Function fn

lib/internal/util.js:477–497

(...args)

  const argumentNames = original[kCustomPromisifyArgsSymbol];

  function fn(...args) {
    return new Promise((resolve, reject) => {
      ArrayPrototypePush(args, (err, ...values) => {
        if (err) {
          return reject(err);
        }
        if (argumentNames !== undefined && values.length > 1) {
          const obj = {};
          for (let i = 0; i < argumentNames.length; i++)
            obj[argumentNames[i]] = values[i];
          resolve(obj);
        } else {
          resolve(values[0]);
        }
      });
      if (isPromise(ReflectApply(original, this, args))) {
        process.emitWarning('Calling promisify on a function that returns a Promise is likely a mistake.',
                            'DeprecationWarning', 'DEP0174');
      }
    });
  }

  ObjectSetPrototypeOf(fn, ObjectGetPrototypeOf(original));