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;
});
This question is related to
javascript
xmlhttprequest
We can check error & 404 statusCode, and use try {} catch (err) {}
.
You can try this :
const req = new XMLHttpRequest();_x000D_
req.onreadystatechange = function() {_x000D_
if (req.status == 404) {_x000D_
console.log("404");_x000D_
return false;_x000D_
}_x000D_
_x000D_
if (!(req.readyState == 4 && req.status == 200))_x000D_
return false;_x000D_
_x000D_
const json = (function(raw) {_x000D_
try {_x000D_
return JSON.parse(raw);_x000D_
} catch (err) {_x000D_
return false;_x000D_
}_x000D_
})(req.responseText);_x000D_
_x000D_
if (!json)_x000D_
return false;_x000D_
_x000D_
document.body.innerHTML = "Your city : " + json.city + "<br>Your isp : " + json.org;_x000D_
};_x000D_
req.open("GET", "https://ipapi.co/json/", true);_x000D_
req.send();
_x000D_
Read more :
This promise will not resolve if the argument of JSON.parse() can not be parsed into a JSON object.
Promise.resolve(JSON.parse('{"key":"value"}')).then(json => {
console.log(json);
}).catch(err => {
console.log(err);
});
You can try this:
Promise.resolve(JSON.parse(response)).then(json => {
response = json ;
}).catch(err => {
response = response
});
I am fairly new to Javascript. But this is what I understood:
JSON.parse()
returns SyntaxError
exceptions when invalid JSON is provided as its first parameter. So. It would be better to catch that exception as such like as follows:
try {
let sData = `
{
"id": "1",
"name": "UbuntuGod",
}
`;
console.log(JSON.parse(sData));
} catch (objError) {
if (objError instanceof SyntaxError) {
console.error(objError.name);
} else {
console.error(objError.message);
}
}
The reason why I made the words "first parameter" bold is that JSON.parse()
takes a reviver function as its second parameter.
Source: Stackoverflow.com