SOURCE

var list = [["27","2.22"],["27","0.0025"],["41","0.003"]];
var results = {};
list.forEach(function(item){
	var id = item[0];
  var value = parseFloat(item[1]);
  if(results[id]==null){
  	value=value;
  }else{
  	value=value+results[id];
  }
  results[id]=value;
})
alert(JSON.stringify(results))