Google Apps script for spreadsheet that groups values in rows

group.js

/**
 * Groups values in rows
 */
function group(vals, test, between){
  vals = purify(vals);
  test = purify(test);
  if(vals.length!=test.length) throw "Vals ("+vals.length+") and Test ("+test.length+") must be of same size";
  
  b = [-Infinity].concat( purify(between) ).concat([Infinity]);

  var ret = [];
  
  for(var g=1; g<b.length; g++){
    ret[g-1] = [];
    for(var i=0; i<test.length; i++){
      if((test[i]>=b[g-1]) && (test[i]<b[g]))ret[g-1].push(vals[i]);
    }
  }
  return ret;
}

function purify(arr){
  var p = [];
  for(var i=arr.length, fst=false; i-->0;){
    if(+arr[i][0]) fst = true;
    if(fst) p[i] = arr[i][0];
  }
  return p;
}