How do I load JSON and split response string?

Question

I have a url that returns JSON, but the beginning of the return string is

])}while(1);</x>{"success":true,"payload":{"value":

I want to split on ])}while(1);</x> and look at the [1] value of the that split array.

Right now I'm doing

fetch(jsonURL)
  .then(res => {
    console.log(res); 
  });

Normally I'd split at the console.log but I'm getting the following error:

the-myth-of-the-genius-programmer-9381a884591e:1 Uncaught (in promise) SyntaxError: Unexpected token ] in JSON at position 0

That looks vaguely like a XSSI-prefix, but what follows after the prefix is not remotely valid JSON. — , Jun 03 '19 at 16:24
@Amy Why isn't it valid JSON? He said it's just the beginning, that's why it's not properly balanced. — Barmar, Jun 03 '19 at 16:27
See https://stackoverflow.com/questions/2669690/why-does-google-prepend-while1-to-their-json-responses before attempting to fix it server side. — John, Jun 03 '19 at 16:51

score 5 · Accepted Answer · answered Jun 03 '19 at 16:25

You need to call response.text() to get the raw text of the response, so you can remove the extraneous stuff at the beginning. Then you have to parse the JSON yourself, you can't use res.json().

fetch(jsonURL)
  .then(res => res.text())
  .then(text => {
    text = text.replace('])}while(1);</x>', '');
    let obj = JSON.parse(text);
    console.log(obj);
|);

This assumes the extraneous stuff is only at the beginning. If there's also something after the JSON, you'll need to remove that as well.

How do I load JSON and split response string?

1 Answers1