react-native fetch example

react-native-fetch.js

const config = require('../config');

async function ajax(path, data, {timeout} = {}) {
  const opts = {
    method: data ? 'POST' : 'GET',
    headers: {
      'Accept': 'application/json',
      'Content-Type': 'application/json'
    },
    credentials: 'same-origin'
  };

  if (data) { 
    opts.body = JSON.stringify(data);
  }
  
  let fetchPromise = fetch(`${config.serverUrl}${path}`, opts);
  let response = await (timeout ? timeoutPromise(timeout, fetchPromise) : fetchPromise);

  if (!response.ok) {    
    let msg = `Request failed. Error code: ${response.status}`;
    if (response.status === 400) {
      try { msg = (await response.json()).error; }
      catch (err) { msg = await response.text(); }
    }
    else if (response.status === 403) { msg = 'Permission denied'; }

    const err = new Error(msg);
    err.status = response.status;
    throw err;
  }

  response = await response.json();

  return response;
}

module.exports = ajax;


function timeoutPromise(ms, promise) {
  return new Promise((resolve, reject) => {
    setTimeout(() => reject(new Error("timeout")), ms);
    promise.then(resolve, reject);
  });
}