public/javascripts/utils/ajax.js

   1 // From JSON (encoded string values!) to "arg1=...&arg2=..."
   2 function toQueryString(data)
   3 {
   4     let data_str = "";
   5     Object.keys(data).forEach(k => {
   6         data_str += k + "=" + encodeURIComponent(data[k]) + "&";
   7     });
   8     return data_str.slice(0, -1); //remove last "&"
   9 }
  10
  11 // data, error: optional
  12 function ajax(url, method, data, success, error)
  13 {
  14     let xhr = new XMLHttpRequest();
  15     if (typeof(data) === "function") //no data
  16     {
  17         error = success;
  18         success = data;
  19         data = {};
  20     }
  21     if (!error)
  22         error = errmsg => { alert(errmsg); };
  23
  24     xhr.onreadystatechange = function() {
  25         if (this.readyState == 4 && this.status == 200)
  26         {
  27             try {
  28                 let res_json = JSON.parse(xhr.responseText);
  29                 if (!res_json.errmsg)
  30                     success(res_json);
  31                 else
  32                     error(res_json.errmsg);
  33             } catch (e) {
  34                 // Plain text (e.g. for rules retrieval)
  35                 success(xhr.responseText);
  36             }
  37         }
  38     };
  39
  40     if (["GET","DELETE"].includes(method) && !!data)
  41     {
  42         // Append query params to URL
  43         url += "/?" + toQueryString(data);
  44     }
  45
  46     xhr.open(method, url, true);
  47     xhr.setRequestHeader('X-Requested-With', "XMLHttpRequest");
  48     if (["POST","PUT"].includes(method))
  49     {
  50         xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
  51         xhr.send(JSON.stringify(data));
  52     }
  53     else
  54         xhr.send();
  55 }