为什么 fetch 总是在这里返回 undefined？

Question

I am working on a Unit Conversion API, and I am having a lot of issues with fetch(). My backend API is working, for example, when I call curl "http://localhost:8000/unitconv/convert?to=lb&from=kg&value=10" I get the correct response: {"units": "lb", "value": 22.04623} . Yet when I do the exact same thing with fetch(), this is what I get: I have tried both localhost and 127.0.0.1 and I still cannot get past this "undefined". What's wrong here?

Answer 1

You are using a curly bracket in the first then without a return so nothing is going to the second then. It should be

.then((response) => {return response.json()}).then(() => ...

Answer 2

You can simply omit the curly brackets like this:

fetch(url).then(response => response.json()).then(() =>