The data received by javascript-fetch from php cannot be parsed using. json (), and the result is always undefined.

Backend code: front-end code: returned data: The statusText is also undefined. In this case, it should be a backend problem. How can I modify the backend code? Thank you!

Backend code:

Front-end code:

Returned data:

Note that statusText is also undefined. In this case, it should be a backend problem. How can I modify the backend?

Thank you!

Reply content:

Backend code:

Front-end code:

Returned data:

Note that statusText is also undefined. In this case, it should be a backend problem. How can I modify the backend?

Thank you!

At the prompt of @ HJin_me, I found that I used {} in the anonymous function. In this way, no data is returned, so the final result is undefined! If there is only one line of code, you can return data without adding {} or returning.

Change break; To exit; try again. Will there be any output.
Can the backend address be opened directly on the webpage to see what the final output is?
Generally, I use firefox and firebug for testing. The returned data is easy to see. The returned data here is not very clear. Maybe I am not used to it.