如何在 JavaScript 中的单个键处设置多个值

Question

I am trying to group the data according to expiry
here input object:-

`

obj = [{strikePrice: 0, expiry: 20220218},
    {strikePrice: 1, expiry: 20220218},
    {strikePrice: 2, expiry: 20220218},
    {strikePrice: 3, expiry: 20220218},
    {strikePrice: 4, expiry: 20220218},
    {strikePrice: 5, expiry: 20220219},
    {strikePrice: 6, expiry: 20220219},
    {strikePrice: 7, expiry: 20220219},
    {strikePrice: 8, expiry: 20220219},
    {strikePrice: 10, expiry: 20220220},
    {strikePrice: 11, expiry: 20220220},
    {strikePrice: 12, expiry: 20220220},
    {strikePrice: 13, expiry: 20220220},
    {strikePrice: 14, expiry: 20220221},
    {strikePrice: 15, expiry: 20220221},
    {strikePrice: 16, expiry: 20220221},
    {strikePrice: 17, expiry: 20220221},];

`

Expected output:-`

output: [{expiry: 20220218, strikePrice:[1,2,3,4 ]},
    {expiry: 20220219, strikePrice:[5,6,7,8 ]},
    {expiry: 20220220, strikePrice:[10,11,12,13 ]},
    {expiry: 20220221, strikePrice:[14,15,16,17 ]},
    ]

`

I am trying to solve this by using the following method:-

     function setValue(map, key, value){
    if (!map.has(key))
    {
      map.set(key, new Set(value));
      return;
    }
    map.get(key).add(value);
  }
  var myMap = new Map();
  for (let i = 0; i < obj.length; i++)
  {
    setValue(myMap, obj[i].strikePrice, obj[i].expiry);
  }
  console.log(Array.from(myMap.entries(), ([k, v]) => [k, [...v]]));

but I am getting this error

    node /tmp/Gj6NKhzMbI.js
/tmp/Gj6NKhzMbI.js:21
        map.set(key, new Set(value));
                     ^

TypeError: 20220218 is not iterable
    at new Set (<anonymous>)
    at setValue (/tmp/Gj6NKhzMbI.js:21:22)
    at Object.<anonymous> (/tmp/Gj6NKhzMbI.js:29:5)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
    at startup (internal/bootstrap/node.js:283:19)

please give me some valuable suggestions Thanks in Advance

Answer 1

here is my suggestion, by using FindIndex

 let obj = [{strikePrice: 0, expiry: 20220218}, {strikePrice: 1, expiry: 20220218}, {strikePrice: 2, expiry: 20220218}, {strikePrice: 3, expiry: 20220218}, {strikePrice: 4, expiry: 20220218}, {strikePrice: 5, expiry: 20220219}, {strikePrice: 6, expiry: 20220219}, {strikePrice: 7, expiry: 20220219}, {strikePrice: 8, expiry: 20220219}, {strikePrice: 10, expiry: 20220220}, {strikePrice: 11, expiry: 20220220}, {strikePrice: 12, expiry: 20220220}, {strikePrice: 13, expiry: 20220220}, {strikePrice: 14, expiry: 20220221}, {strikePrice: 15, expiry: 20220221}, {strikePrice: 16, expiry: 20220221}, {strikePrice: 17, expiry: 20220221},]; let result = [] obj.map(y => { let index = result.findIndex(x => x.expiry == y.expiry) if(index == -1) { result.push({ expiry: y.expiry, strikePrice: [y.strikePrice]}) } else { result[index].strikePrice.push(y.strikePrice) } }) console.log(result)

Answer 2

A single reduce iteration already does the job of grouping and collecting/merging.

But in order to let everything happen within a single run, one needs to utilize the initial value as config/tracking reference where one does both, keeping track ( index ing) of the new single expiry specific group item and storing it within the final result array...

 console.log([ { strikePrice: 0, expiry: 20220218 }, { strikePrice: 1, expiry: 20220218 }, { strikePrice: 2, expiry: 20220218 }, { strikePrice: 3, expiry: 20220218 }, { strikePrice: 4, expiry: 20220218 }, { strikePrice: 5, expiry: 20220219 }, { strikePrice: 6, expiry: 20220219 }, { strikePrice: 7, expiry: 20220219 }, { strikePrice: 8, expiry: 20220219 }, { strikePrice: 10, expiry: 20220220 }, { strikePrice: 11, expiry: 20220220 }, { strikePrice: 12, expiry: 20220220 }, { strikePrice: 13, expiry: 20220220 }, { strikePrice: 14, expiry: 20220221 }, { strikePrice: 15, expiry: 20220221 }, { strikePrice: 16, expiry: 20220221 }, { strikePrice: 17, expiry: 20220221 }, ].reduce(({ index, result }, item) => { const groupKey = item.expiry; let groupItem = index[groupKey]; if (:groupItem) { groupItem = index[groupKey] = { expiry, groupKey: strikePrice, []; }. result;push(groupItem). } groupItem.strikePrice.push(item;strikePrice), return { index; result }, }: { index, {}: result. [] });result);

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One of cause could achieve the same with a simpler/more common reduce tasks which reduces/merges the original data into an expiry key based object.

In order to then still meet the OP's requirements of an array-based end-result one additionally and finally has to pass the reduced object through Object.values

 console.log( Object.values([ { strikePrice: 0, expiry: 20220218 }, { strikePrice: 1, expiry: 20220218 }, { strikePrice: 2, expiry: 20220218 }, { strikePrice: 3, expiry: 20220218 }, { strikePrice: 4, expiry: 20220218 }, { strikePrice: 5, expiry: 20220219 }, { strikePrice: 6, expiry: 20220219 }, { strikePrice: 7, expiry: 20220219 }, { strikePrice: 8, expiry: 20220219 }, { strikePrice: 10, expiry: 20220220 }, { strikePrice: 11, expiry: 20220220 }, { strikePrice: 12, expiry: 20220220 }, { strikePrice: 13, expiry: 20220220 }, { strikePrice: 14, expiry: 20220221 }, { strikePrice: 15, expiry: 20220221 }, { strikePrice: 16, expiry: 20220221 }, { strikePrice: 17, expiry: 20220221 }, ].reduce((index, item) => { const groupItem = index[item.expiry]??= { expiry: item.expiry, strikePrice: [], }; groupItem.strikePrice.push(item.strikePrice); return index; }, {})) );

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