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 (data === undefined || typeof(data) === "function") //no data
  21     {
  22         error = success;
  23         success = data;
  24         data = {};
  25     }
  26   if (!success)
  27     success = () => {}; //by default, do nothing
  28     if (!error)
  29         error = errmsg => { alert(errmsg); };
  30     xhr.onreadystatechange = function() {
  31         if (this.readyState == 4 && this.status == 200)
  32         {
  33       let res_json = "";
  34             try {
  35                 res_json = JSON.parse(xhr.responseText);
  36       } catch (e) {
  37                 // Plain text (e.g. for rules retrieval)
  38                 return success(xhr.responseText);
  39       }
  40       if (!res_json.errmsg)
  41         success(res_json);
  42             else
  43                 error(res_json.errmsg);
  44         }
  45     };
  46
  47     if (["GET","DELETE"].includes(method) && !!data)
  48     {
  49         // Append query params to URL
  50         url += "/?" + toQueryString(data);
  51     }
  52     xhr.open(method, params.serverUrl + url, true);
  53     xhr.setRequestHeader('X-Requested-With', "XMLHttpRequest");
  54     // Next line to allow cross-domain cookies in dev mode (TODO: if...)
  55   if (params.cors)
  56     xhr.withCredentials = true;
  57   if (["POST","PUT"].includes(method))
  58     {
  59         xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
  60         xhr.send(JSON.stringify(data));
  61     }
  62     else
  63         xhr.send();
  64 }