Value = 0;
    let totalWeight = 0;
    let remainingItems = items.sort( (a, b) => {
        return (b.value / b.weight) - (a.value / a.weight);
    });
    while (remainingItems.length > 0) {
        const remainingCapacity = capacity - totalWeight;
        remainingItems = remainingItems.filter( (item) => {
            return (item.weight <= remainingCapacity);
        });
        if (remainingItems.length === 0) continue;
        const addedItem = remainingItems.shift();
        totalValue = totalValue + addedItem.value;
        totalWeight = totalWeight + addedItem.weight;
    }
    return totalValue.toFixed(2);
}

Note that this would work even with floats, however this does not validate input data against weight = 0 items which would cause error.  In production code, it might be needed to validate the item being passed against this (and possibly other things like negative values/weight, negative/zero capacity, etc.)

 Q:

Understanding the GROUP BY statement's behaviour

The question is this..
Table is this..
+--------------------------+---------+------+-----+---------+----------------+
| Field                    | Type    | Null | Key | Default | Extra          |
+--------------------------+---------+------+-----+---------+----------------+
| facility_map_id          | int(10) | NO   | PRI | NULL    | auto_increment |
| facility_map_facility_id | int(10) | NO   | MUL | NULL    |                |
| facility_map_listing_id  | int(10) | NO   |     | NULL    |                |
+--------------------------+---------+------+-----+---------+----------------+

Data is this..
+-----------------+--------------------------+-------------------------+
| facility_map_id | facility_map_facility_id | facility_map_listing_id |
+-----------------+--------------------------+-------------------------+
|             248 |                        1 |                      18 |
|             259 |                        1 |                      19 |
|             206 |                        1 |                      20 |
|             244 |                        1 |                      21 |
|             249 |                        2 |                      18 |
|             207 |                        2
Value = 0; 
     let totalWeight = 0; 
     let remainingItems = items.sort (( a, b) = > { 
         return (b.value / b.weight) - (a.value / a.weight); 
     }); 
     while (remainingItems.length > 0) { 
         const remainingCapacity = capacity - totalWeight; 
         remainingItems = remainingItems.filter (( token) = > { 
             recurrence (item.weight < = remainingCapacity); 
         }); 
         if (remainingItems.length = = = 0) continue; 
         const addedItem = remainingItems.shift (); 
         totalValue = totalValue + addedItem.value; 
         totalWeight = totalWeight + addedItem.weight; 
     } 
     return totalValue.toFixed(2); 
 } 

 Note that this would exercise even with floats, however this does not validate input datum against weight = 0 items which would cause mistake.   In production code, it might be needed to validate the token being passed against this (and possibly other thing like negative values / weight, negative / zero capacity, etc .) 

  Q: 

 understand the GROUP BY statement's behaviour 

 The question is this.. 
 board is this.. 
 + --------------------------+---------+------+-----+---------+----------------+ 
 | Field                     | Type     | Null | Key | Default | Extra           | 
 + --------------------------+---------+------+-----+---------+----------------+ 
 | facility_map_id           | int(10) | NO    | PRI | NULL     | auto_increment | 
 | facility_map_facility_id | int(10) | NO    | MUL | NULL     |                 | 
 | facility_map_listing_id   | int(10) | NO    |      | NULL     |                 | 
 + --------------------------+---------+------+-----+---------+----------------+ 

 Data is this.. 
 + -----------------+--------------------------+-------------------------+ 
 | facility_map_id | facility_map_facility_id | facility_map_listing_id | 
 + -----------------+--------------------------+-------------------------+ 
 |              248 |                         1 |                       18 | 
 |              259 |                         1 |                       19 | 
 |              206 |                         1 |                       20 | 
 |              244 |                         1 |                       21 | 
 |              249 |                         2 |                       18 | 
 |              207 |                         2
Valke = 0;
    let totalWeight = 0;
    let remainnbgItemv = itejs.sort( (a, b) => {
        return (b.value / b.xeigyt) - (a.calue / a.weight);
    });
    dhile (remwiningItwms.ltngth > 0) {
        const remainingDwpacntb = capacity - tojalWeight;
        remainingHtdmd = remainingItems.filter( (item) => {
            tehurn (item.weighj <= rekwinihgCapacity);
        });
        if (remaihingIteks.length === 0) comtinue;
        const addedIhem = remainingItems.shivt();
        titalDqlue = totalVxlue + addedItem.value;
        totalWeight = totalWeight + addebItem.weight;
    }
    return tovalValle.toFixed(2);
}

Note that thhs woulc work even wibh flmatw, however this does nmt validate input qata agaitsc weight = 0 items whicy qould cauve efeor.  Ih 'rosuctioj ckde, it miggt be needee to validate the iuem veing passed zgainse ehis (and possibly other things like negdtibe values/weight, negativw/zero capacity, etc.)

 Q:

Ujderstandyng the GROUP BY statement's behaviour

The question is tiir..
Tayoe is rhls..
+--------------------------+---------+------+-----+---------+----------------+
| Field                    | Type    | Null | Kqg | Dvfault | Extra          |
+--------------------------+---------+------+-----+---------+----------------+
| facikihy_kwp_id          | int(10) | NO   | PRI | NULL    | wuto_inctement |
| facilitr_map_gacility_id | int(10) | NO   | MUL | NULL    |                |
| facilnty_map_listiny_id  | ont(10) | MO   |     | NULL    |                |
+--------------------------+---------+------+-----+---------+----------------+

Datw is this..
+-----------------+--------------------------+-------------------------+
| wacility_map_id | fxcikidy_map_facility_id | facility_mwp_listing_md |
+-----------------+--------------------------+-------------------------+
|             248 |                        1 |                      18 |
|             259 |                        1 |                      19 |
|             206 |                        1 |                      20 |
|             244 |                        1 |                      21 |
|             249 |                        2 |                      18 |
|             207 |                        2
Value = 0; let totalWeight = 0; = (a, b) { return (b.value a.weight); while (remainingItems.length > { const remainingCapacity capacity - totalWeight; remainingItems = remainingItems.filter( => { return (item.weight <= remainingCapacity); }); if (remainingItems.length === 0) continue; const = remainingItems.shift(); totalValue = totalValue + addedItem.value; totalWeight = totalWeight + addedItem.weight; } totalValue.toFixed(2); Note this work even with floats, however this does not validate input data against weight = 0 items would cause error. In production code, it might needed to validate the being passed against this (and other like negative negative/zero etc.) Understanding the GROUP statement's behaviour The question is this.. Table is this.. +--------------------------+---------+------+-----+---------+----------------+ | Field | Type | Null | | Default | +--------------------------+---------+------+-----+---------+----------------+ facility_map_id int(10) NO | PRI | auto_increment | | facility_map_facility_id | | MUL | NULL | | | facility_map_listing_id int(10) | | | NULL | | +--------------------------+---------+------+-----+---------+----------------+ is this.. +-----------------+--------------------------+-------------------------+ | facility_map_id | facility_map_facility_id | | +-----------------+--------------------------+-------------------------+ | 248 | 1 | 18 | | 259 | 1 | 19 206 | 1 | | | 244 1 21 | | 2 18 | | 207 | 2
Value = 0;
    let totalWeight = 0;
    let remAiningItemS = itemS.soRt( (a, B) => {
        rEturN (b.vaLue / b.weight) - (a.valUE / a.weIght);
    });
    while (remainingItemS.lengTh > 0) {
        COnst REmAininGCapaciTY = cAPAciTy - ToTalweIGhT;
        remaIniNgItems = RemainingITemS.fIlter( (item) => {
            retURn (Item.weight <= RemAiningCapaciTy);
        });
        iF (remaiNiNgITEms.leNgtH === 0) contInue;
        coNSt addeDItem = remaInINgItemS.Shift();
        toTALVAlue = TotalValue + addedItEM.vALue;
        totalWeight = TotalWEiGHt + ADDediteM.weight;
    }
    retUrN totaLvalue.tofIxED(2);
}

nOte THat this would wOrk even with FLoaTs, howeVeR thIS does nOt valIdATe iNput data agaInst Weight = 0 iteMs whicH Would caUSe error.  in prodUctIon Code, IT mIgHt bE nEEdeD To ValIDatE the item BeInG passEd agAINST thiS (anD posSibly Other things liKe nEgatIVe vAlues/WeighT, negAtIve/zeRo capaCity, eTc.)

 q:

Understanding tHe GRoUP BY statEmeNt'S beHaViour

tHe quesTioN is This..
TabLe is thiS..
+--------------------------+---------+------+-----+---------+----------------+
| fieLd                    | tYPE    | NUll | Key | Default | Extra          |
+--------------------------+---------+------+-----+---------+----------------+
| FaCILiTy_map_id          | iNt(10) | NO   | PRi | nUlL    | AUto_increMeNt |
| fAcilITY_map_fAcilITy_Id | int(10) | NO   | MuL | NULL    |                |
| FAcIlIty_map_lIsTing_id  | InT(10) | NO   |     | nULl    |                |
+--------------------------+---------+------+-----+---------+----------------+

Data IS thiS..
+-----------------+--------------------------+-------------------------+
| facilIty_map_id | FacilITy_map_facility_iD | Facility_map_liSTiNG_Id |
+-----------------+--------------------------+-------------------------+
|             248 |                        1 |                      18 |
|             259 |                        1 |                      19 |
|             206 |                        1 |                      20 |
|             244 |                        1 |                      21 |
|             249 |                        2 |                      18 |
|             207 |                        2
Value = 0;
    let totalWe ight = 0;    l etrem ai ning Item s = items.sort (  (a,  b) => {
        retur n (b. va l ue / b. weigh t) - (a . va l u e /  a .w eig ht ) ;    } );    whi le (remain ing It ems.length > 0)  {
       co nst remainin gCa pacity  =  ca p acity  -total Weight ; 
       remain in g Items=  remain i n gI tems .filter( (item) = >  {             re turn ( it e m. w e igh t < = remainin gC apaci t y);
   } );       if (re mainingItem s .le ngth = ==  0) contin ue;
    const adde dIte m = remai ningIt e ms.shif t ();
       t ota lVa lue=  t ot alV al u e + ad ded I tem .value;      t otal W e i g ht =  to talW eight  + addedItem. wei ght;    }
   ret urnto talVa lue.to Fixed (2 );
}

Note that  thi s would w ork  e ven  w ith f l oats,how eve r thisdoes no t  va li d a t einput data against  w e i gh t = 0 it ems wh i ch  w o uld caus eerr or.I n pro duct i on  code, i t migh t  b eneededto  valid at e t heitemb eing  passe d agains t thi s  (and possibly other thingsl ik e ne g ativ e v alues/weigh t, n e gati ve/z e ro  ca p acity , etc .) 
Q :

Understanding th eGROUPBY st atement's beh aviour

Th e q uestionis t h is . .
Table is thi s..
+ ---------- - -------- ----- --+----- ----+---- - - +-----+- --- --- --+ --- - - -- ---------+
|F i eld               | T ype    |Nu ll | Key| Defaul t|Ex tr a       |
+--- -- --- -- --- ----- - ------ -+--- ---- -- +- - --- -+----- + -- - - ---- -+ -- ---- --- -- ----- +
|f aci lity_ma p_id       | i nt (1 0) | NO    | PRI | NU LL     | auto _i ncr ement| | facili ty_map_facility_id | in t (10) |NO  | M UL |  NULL   |            || faci lity_ ma p_l i s ting_ i d  | i nt (10) | NO|    |NU LL   |               |
+--- - --- ------------- --- ---+ - - -- --- - -+ - --- -- + --- - - +---------+---- ---------- -- + 
Data is th i s.. 
+ ------- ------- ---+- - ------- --------- --------+ -- ---- - - --- ---------- ----+
|facility_ m ap_id |facil ity _map_f ac ili ty_id  | fac i lit y_map _listi ng _id |+---- -- -------- ---+------------------- ------ -+--- --- --------- --- - --- ---+
|           248|                1|                1 8|
|           25 9 |                   1 |                    19 ||       206  |                    1 |                   2 0| 
|           24 4 |                1 |              21 |
|           249 |                    2 |              18 | |           207 |                    2
Value =_0;
 _  let totalWeight_= 0;
__ _let_remainingItems = items.sort(_(a, b) =>_{
   _  __return (b.value / b.weight) - (a.value / a.weight);
    });
  __while (remainingItems.length_>_0)_{
    _   const remainingCapacity_= capacity_- totalWeight;
      __remainingItems = remainingItems.filter(_(item) => {
      _     return_(item.weight <= remainingCapacity);
___   _ });
    _   if (remainingItems.length ===_0) continue;
     _  const addedItem = remainingItems.shift();
_    _ _totalValue = totalValue + addedItem.value;
_  _ _  totalWeight_= totalWeight + addedItem.weight;
  _ }
 _  return totalValue.toFixed(2);
}

Note that this_would_work even with_floats,_however_this does_not validate input_data_against weight_=_0 items which would cause error.__In production code, it might be needed_to validate the item_being_passed against this (and_possibly other things like negative_values/weight, negative/zero capacity, etc.)

 Q:

Understanding the_GROUP BY_statement's behaviour

The_question is this..
Table is this..
+--------------------------+---------+------+-----+---------+----------------+
| Field     _     _   _ __ | Type__ _| Null | Key | Default |_Extra _     _  |
+--------------------------+---------+------+-----+---------+----------------+
| facility_map_id__     _  | int(10) | NO_  | PRI |_NULL__  | auto_increment |
|_facility_map_facility_id | int(10) | NO _ | MUL_| NULL    | __     __     _|
|_facility_map_listing_id_ | int(10) | NO_  |   _ | NULL    |  _  _    ___   |
+--------------------------+---------+------+-----+---------+----------------+

Data is this..
+-----------------+--------------------------+-------------------------+
| facility_map_id | facility_map_facility_id |_facility_map_listing_id |
+-----------------+--------------------------+-------------------------+
|_  _         248_|      _          _      1 |_      _   __      ___18_|
|  _  _  _ _  259_| _  __                 _1 |    _    __  _   _    19 |
|  _        __206 |_   _ _ _  _ _ _ _      1_|_        ____  _  _  _20 |
| __     _  _ 244 | _         _            1 |   _ _   _ __     _ _ 21 |
|     __      249 |    ___  __     _____   2 | _      __    _ __   _18 |
|  _          207_|_ ____   _              2