[hostoptus]

В чём косяк вроде правильно, должен выдать все id бойцов клана.

function file_get_contents( url ) { // Reads entire file into a string
 // 
 // + original by: Legaev Andrey
 // % note 1: This function uses XmlHttpRequest and cannot retrieve resource from different domain.

 var req = null;
 try { req = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {
 try { req = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {
 try { req = new XMLHttpRequest(); } catch(e) {}
 }
 }
 if (req == null) throw new Error('XMLHttpRequest not supported');

 req.open("GET", url, false);
 req.send(null);

 return req.responseText;
}
var mydata = file_get_contents('http://api.worldoftanks.ru/wgn/clans/info/?application_id=demo&clan_id=195497');
mydata = JSON.parse (mydata);
var val = mydata['data']['195497']['members'];
val.forEach(function(item, i, val) {
  var dt = item;
  document.write( i + ": " + dt[account_id]);
});