group items of list by proprety value js
function groupBy(collection, property) {
var i = 0, val, index,
values = [], result = [];
for (; i < collection.length; i++) {
val = collection[i][property];
index = values.indexOf(val);
if (index > -1)
result[index].push(collection[i]);
else {
values.push(val);
result.push([collection[i]]);
}
}
return result;
}
var obj = groupBy(list, "group");
//https://stackoverflow.com/questions/21776389/javascript-object-grouping