Fetch with react native - api

Question

I am using fetch in React Native in order to make a call to my API, however, it only works 75% of the time.
When my request doesn't work I get this :
TypeError: Network request failed
or
SyntaxError: Unexpected token < in JSON at position 0
fetch('http://localhost/vision.php', {
method: 'POST',
headers: {
'Accept': 'application.json',
'Content-Type': 'application.json',
},
body: JSON.stringify({
key: 'Mon paramètre'
})
})
.then((data) => data.json())
.then((dataJson) => {
console.log(dataJson.message);
})
.catch((error) => {
console.log(error);
});
}
Someone can explain that ?

Answer 1

When you get TypeError: Network request failed, it means that, well, the network request failed. It could mean the API / server you're trying to connect to is down / not listening for connections anymore.
Regarding SyntaxError: Unexpected token < in JSON at position 0, that's what you get when trying to parse non-JSON as JSON. Typically here it's likely your API / server failing to fulfill your request and, instead of JSON, serving you an HTML error page.
You might want to check if data.ok is true before trying to parse the JSON response (data.json()).