javascript - push string from ajax to array for AmCharts -

hi i'm noob in javascript , need help. want draw chart real time data mcu. don't know how push string array. in code array (chart.dataprovider) still undefined

var chart = amcharts.makechart("chartdiv",{  ...  "dataprovider":[], });  function f() {       var req = new xmlhttprequest();      req.onreadystatechange = function() {      if (this.readystate == 4 && this.status == 200) {      var value = this.responsetext;        //get response data string                  //  value= {cat: 1, c1: 2, c2: 3};    //this metod draw chart want rt data...      alert(value); //output: {cat: 1, c1: 2, c2: 3}      chart.dataprovider.push(value);      chart.validatedata();                                                       }};      req.open("get", "http://", true);      req.send();      } 

also works too:

chart.dataprovider.push({ cat: 1, c1: 2, c2: 3 }); 

but how push data xmlhttprequest?

you need initialize chart.dataprovider = [] before pushing new values.

if problematic - check if it's undefined, , if - initialize chart.dataprovider = chart.dataprovider? chart.dataprovider : []

lastly, if question regarding ajax operation - try use promises or callback wait push operation.

hope helps