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Networking
Many mobile apps need to load resources from a remote URL. You may want to make a POST request to a REST API, or you may simply need to fetch a chunk of static content from another server.
Using Fetch
React Native provides the Fetch API for your networking needs. Fetch will seem familiar if you have used XMLHttpRequest or other networking APIs before. You may refer to MDN's guide on Using Fetch for additional information.
Making requests
In order to fetch content from an arbitrary URL, just pass the URL to fetch:
fetch('https://mywebsite.com/mydata.json');
Fetch also takes an optional second argument that allows you to customize the HTTP request. You may want to specify additional headers, or make a POST request:
The above examples show how you can make a request. In many cases, you will want to do something with the response.
Networking is an inherently asynchronous operation. Fetch methods will return a Promise that makes it straightforward to write code that works in an asynchronous manner:
The XMLHttpRequest API is built in to React Native. This means that you can use third party libraries such as frisbee or axios that depend on it, or you can use the XMLHttpRequest API directly if you prefer.
The security model for XMLHttpRequest is different than on web as there is no concept of CORS in native apps.
WebSocket Support
React Native also supports WebSockets, a protocol which provides full-duplex communication channels over a single TCP connection.
var ws =newWebSocket('ws://host.com/path');
ws.onopen=()=>{// connection opened
ws.send('something');// send a message};
ws.onmessage=(e)=>{// a message was received
console.log(e.data);};
ws.onerror=(e)=>{// an error occurred
console.log(e.message);};
ws.onclose=(e)=>{// connection closed
console.log(e.code, e.reason);};