#System.formatexception visual micro how to

You might have a typo in the client code ( /users instead of /user) or in the server code that sets up the route. The URL doesnвЂ™t exist and the server returned an 404 page as HTML.The server might return HTML instead of JSON for a bunch of reasons: log ( someString ) // log out out, and see what's wrong Blame the Server? JSON.parse(someString) // comment this out temporarily console. Alter your code to read something like this, and check the console to see whatвЂ™s causing the problem:

With fetch, you can use res.text() instead of res.json() to get the text string itself. The first thing to do is try logging it out.

#System.formatexception visual micro how to

Watch the video above for how this error works, and how to use your browserвЂ™s developer tools to figure out exactly whatвЂ™s causing it.

Unexpected token d in JSON at position 0.

Unexpected token p in JSON at position 0.

Unexpected token < in JSON at position 1.

Here are some other variations IвЂ™ve seenвЂ¦ The token and the position may vary, but the root cause is the same: the text that your app is trying to parse as JSON is not actually valid JSON. The exact text of this error will differ depending on what the server returned. Why would it do that? вЂњUnexpected token o in JSON at position 1вЂќ and other varieties The root cause is that the server returned HTML or some other non-JSON string. That unexpected token, <, is a strong clue that the response was HTML instead of JSON. This response started with a < (hence the вЂњUnexpected token <вЂќ). JSON should start with a valid JSON value вЂ“ an object, array, string, number, or false/ true/ null. JSON.parse is what fetchвЂ™s res.json() is doing under the hood, so the error will be the same either way.