Voir https://stackoverflow.com/questions/
21811630/splicing-a-javascript-array-from-within-the-callback-passed-to-foreach
 
 BwDrawer.draw_bandwidth_graph = function(raw_data, selector, period) {
   // Purge non running relays
-  raw_data.relays.forEach(function(r, i) {
-    if (typeof r.read_history === 'undefined' || typeof r.write_history === 'undefined') {
-      raw_data.relays.splice(i, 1);
-    }
+  raw_data.relays = raw_data.relays.filter(function(relay) {
+    return typeof r.read_history === 'undefined' || typeof r.write_history === 'undefined';
   });
 
+
   var update_period;
 
   var svg = d3.select(selector).append("svg")