client/src/utils/ajax.js

   1 import params from "../parameters"; //for server URL
   2
   3 // TODO: replace by fetch API ?
   4 // https://www.sitepoint.com/xmlhttprequest-vs-the-fetch-api-whats-best-for-ajax-in-2019/
   5
   6 // From JSON (encoded string values!) to "arg1=...&arg2=..."
   7 function toQueryString(data)
   8 {
   9     let data_str = "";
  10     Object.keys(data).forEach(k => {
  11         data_str += k + "=" + encodeURIComponent(data[k]) + "&";
  12     });
  13     return data_str.slice(0, -1); //remove last "&"
  14 }
  15
  16 // data, error: optional
  17 export function ajax(url, method, data, success, error)
  18 {
  19     let xhr = new XMLHttpRequest();
  20     if (typeof(data) === "function") //no data
  21     {
  22         error = success;
  23         success = data;
  24         data = {};
  25     }
  26     if (!error)
  27         error = errmsg => { alert(errmsg); };
  28
  29     xhr.onreadystatechange = function() {
  30         if (this.readyState == 4 && this.status == 200)
  31         {
  32       let res_json = "";
  33             try {
  34                 res_json = JSON.parse(xhr.responseText);
  35       } catch (e) {
  36                 // Plain text (e.g. for rules retrieval)
  37                 return success(xhr.responseText);
  38       }
  39       if (!res_json.errmsg)
  40         success(res_json);
  41             else
  42                 error(res_json.errmsg);
  43         }
  44     };
  45
  46     if (["GET","DELETE"].includes(method) && !!data)
  47     {
  48         // Append query params to URL
  49         url += "/?" + toQueryString(data);
  50     }
  51     xhr.open(method, params.serverUrl + url, true);
  52     xhr.setRequestHeader('X-Requested-With', "XMLHttpRequest");
  53     // Next line to allow cross-domain cookies in dev mode (TODO: if...)
  54   if (params.cors)
  55     xhr.withCredentials = true;
  56   if (["POST","PUT"].includes(method))
  57     {
  58         xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
  59         xhr.send(JSON.stringify(data));
  60     }
  61     else
  62         xhr.send();
  63 }