Proper way to catch exception from JSON.parse

Question

I’m using JSON.parse on a response that sometimes contains a 404 response. In the cases where it returns 404, is there a way to catch an exception and then execute some other code?

data = JSON.parse(response, function (key, value) {     var type;     if (value && typeof value === 'object') {         type = value.type;         if (typeof type === 'string' && typeof window[type] === 'function') {             return new(window[type])(value);         }     }     return value; }); 

Answer 1

i post something into an iframe then read back the contents of the iframe with json parse...so sometimes it's not a json string

Try this:

if(response) {     try {         a = JSON.parse(response);     } catch(e) {         alert(e); // error in the above string (in this case, yes)!     } } 

Answer 2

We can check error & 404 statusCode, and use try {} catch (err) {}.

You can try this :

const req = new XMLHttpRequest();  req.onreadystatechange = function() {      if (req.status == 404) {          console.log("404");          return false;      }        if (!(req.readyState == 4 && req.status == 200))          return false;        const json = (function(raw) {          try {              return JSON.parse(raw);          } catch (err) {              return false;          }      })(req.responseText);        if (!json)          return false;        document.body.innerHTML = "Your city : " + json.city + "<br>Your isp : " + json.org;  };  req.open("GET", "https://ipapi.co/json/", true);  req.send();

Read more :

• Catch a 404 error for XHR