为什么异步/等待变量返回未定义？

Question

Below is my code...

async function getItemDetalil(url) {
  const $ = await request(url, (err, res, body) => {
      return cheerio.load(body);
  });
  console.log($);
}

Why my '$' is undefined? I assume it will be a cheerio object?

Answer 1

Why async/await variable return undefined?

await x evaluates to the value of x or, if that value is a promise, to the value the promise resolves to.

Example:

 // Value (async function() { console.log('Normal value', await 42); }()); // Promise resolution (async function() { console.log('From promise:', await Promise.resolve(42)); }()); 

If $ is undefined , then request() either returns undefined or a promise that resolves to undefined (unlikely). Have a look at its documentation or source code to find out what exactly is happening.

---

I assume it will be a cheerio object?

It would only be cherrio object iff request actually returns a cherrio object or a promise that resolves to a cherrio object.

How do I convert an existing callback API to promises? might help you to solve your actual coding problem.