InfoVis Treemap来自另一个文件的动态数据

Question

我有来自示例1.js的代码（链接在下面给出） 这里变量json包含json数据，而不是在此文件中指定此数据，我想从另一个文件中引用，这将有助于我使protovis树形图动态化。

我是json的新手我不知道如何将来自另一个文件的商店json数据引用到变量中 完整代码可在此链接http://thejit.org/static/v20/Jit/Examples/Treemap/example1.js

中找到

 function init(){
 //init data
  var json = {
 "children": [
 {
   "children": [
     {
       "children": [], 
       "data": {
         "playcount": "276", 
         "$color": "#8E7032", 
         "image": "http://userserve-ak.last.fm/serve/300x300/11403219.jpg", 
         "$area": 276
       }, 
       "id": "album-Thirteenth Step", 
       "name": "Thirteenth Step"
     }, 
     {
       "children": [], 
       "data": {
         "playcount": "271", 
         "$color": "#906E32", 
         "image": "http://userserve-ak.last.fm/serve/300x300/11393921.jpg", 
         "$area": 271
       }, 
       "id": "album-Mer De Noms", 
       "name": "Mer De Noms"
     }
   ], 
   "data": {
     "playcount": 547, 
     "$area": 547
   }, 
   "id": "artist_A Perfect Circle", 
   "name": "A Perfect Circle"
 }, 
 {
   "children": [
     {
       "children": [], 
       "data": {
         "playcount": "209", 
         "$color": "#AA5532", 
         "image": "http://userserve-ak.last.fm/serve/300x300/32349839.jpg", 
         "$area": 209
       }, 
       "id": "album-Above", 
       "name": "Above"
     }
   ], 
   "data": {
     "playcount": 209, 
     "$area": 209
   }, 
   "id": "artist_Mad Season", 
   "name": "Mad Season"
 }
  ......