title: "group by" on json data (special structure)
body: <p>I've data from students in json that I need to <strong>sumup by types (here below EP) and show as percentage</strong> of the maximum score, using only javascript.</p>
  
  <pre><code>{
  "document_title":"NOTE",
  "teacher_name":"AM",
  "assignments":[
      {
          "date":"15 jan. 2014",
          "abbr":"EP1",
          "title":"Epreuve 1",
          "type":"EP",
          "max":"100"
      },{
          "date":"16 jan. 2014",
          "abbr":"EP2",
          "title":"Epreuve 2",
          "type":"EP",
          "max":"60"
      }],
  "students":[
      {
          "name":"Apprenant 1",
          "points":["75","47"]
      },{
          "name":"Apprenant 2",
          "points":["18","35"]
      },{
          "name":"Apprenant 3",
          "points":["95","57"]
      },{
          "name":"Apprenant 4",
          "points":["60","26"]
      }],
  "history":[],
  "history_index":0
  }
  </code></pre>
  
  <p>I can't figure out how to do ...</p>