Javascript-fetch data received from PHP is not resolved through. JSON (), and the result is always undefined

Back-End Code:

Front-End Code:

The returned data:

Note that statustext is also undefined, this situation, should be the problem of the backend, ask, how to modify the backend?

Thank you!

Reply content:

Back-End Code:

Front-End Code:

The returned data:

Note that statustext is also undefined, this situation, should be the problem of the backend, ask, how to modify the backend?

Thank you!

At @hjin_me's prompt, I found myself using {} in the anonymous function, so that the data is not returned, so the final result is undefined! If there is only one line of code, you can return the data without adding {}, and you don't need a return.

Break, change to exit, try, will also have east output.
Can the backend address be opened directly in the Web page to see what the final output is?
General test I use Firefox and Firebug, the returned data is easy to see, the return data here is not very clear, may be I am not used to.

