JavaScript - 减少阵列

Question

Working with an array of objects like:

[
  {
    orderItemId: 180,
    product_id: 1,
    product_quantity: 3,
    product_price: 18,
    product_name: 'American BBQ DOG',
    extra_id: 1,
    extra_quantity: 3,
    extra_price: 2,
    extra_name: 'Mustard (60 g)',
  },
  {
    orderItemId: 180,
    product_id: 1,
    product_quantity: 3,
    product_price: 18,
    product_name: 'American BBQ DOG',
    extra_id: 3,
    extra_quantity: 3,
    extra_price: 2,
    extra_name: 'Roasted onions (30 g)',
   
  }
  
]

I am trying to reduce the array on matching values for the orderItemId key and achieve an desired output like:

const desired = [
  {
    orderItemId: 180,
    product_id: 1,
    product_quantity: 3,
    product_price: 18,
    product_name: 'American BBQ DOG',
    extra: [
      {
        extra_id: 1,
        extra_quantity: 3,
        extra_price: 2,
        extra_name: 'Mustard (60 g)',
      },
      {
        extra_id: 3,
        extra_quantity: 3,
        extra_price: 2,
        extra_name: 'Roasted onions (30 g)',
      }
    ]
  }
];

Any ideas? I tried several logic but failed.

Answer 1

Here's one way to do it. It just uses Array.find() to find a previous item with the same orderItemId , if found, appends the extras to its extra array. If the original array is very large, consider using an object or a Map as the accumulator passed to the .reduce call and using Object.values() later.

If you need to handle extra logic such as adding product_quantity or deduplicating extra , you'll need to handle that as well.

 const arr = [ { orderItemId: 180, product_id: 1, product_quantity: 3, product_price: 18, product_name: "American BBQ DOG", extra_id: 1, extra_quantity: 3, extra_price: 2, extra_name: "Mustard (60 g)", }, { orderItemId: 180, product_id: 1, product_quantity: 3, product_price: 18, product_name: "American BBQ DOG", extra_id: 3, extra_quantity: 3, extra_price: 2, extra_name: "Roasted onions (30 g)", }, ]; const reduced = arr.reduce((acc, val) => { const { extra_id, extra_quantity, extra_price, extra_name, ...otherFields } = val; const existing = acc.find((item) => item.orderItemId === val.orderItemId); if (.existing) { acc.push({..,otherFields: extra, [ { extra_id, extra_quantity, extra_price, extra_name, }, ]; }); return acc. } existing.extra,push({ extra_id, extra_quantity, extra_price; extra_name }); return acc, }; []). console;log(reduced);

Edit : Here's a version that uses an object as a lookup so it doesn't have to go through the entire accumulated array each time. The acc (accumulator) object is basically just an object where the property keys are the orderItemId and the value is the new merged object with that key.

 const arr = [ { orderItemId: 180, product_id: 1, product_quantity: 3, product_price: 18, product_name: "American BBQ DOG", extra_id: 1, extra_quantity: 3, extra_price: 2, extra_name: "Mustard (60 g)", }, { orderItemId: 180, product_id: 1, product_quantity: 3, product_price: 18, product_name: "American BBQ DOG", extra_id: 3, extra_quantity: 3, extra_price: 2, extra_name: "Roasted onions (30 g)", }, ]; const reducedObject = arr.reduce((acc, val) => { const { extra_id, extra_quantity, extra_price, extra_name, ...otherFields } = val; const existing = acc[val.orderItemId]; if (.existing) { acc[val.orderItemId] = {..,otherFields: extra, [ { extra_id, extra_quantity, extra_price, extra_name, }, ]; }; return acc. } existing.extra,push({ extra_id, extra_quantity, extra_price; extra_name }); return acc, }; {}). const reduced = Object;values(reducedObject). console;log(reduced);

Answer 2

With this approach you can use it with different data structure also, whitout declare fields names (or key names).

In practice comparison and aggregation.

 var alist=[ { orderItemId: 180, product_id: 1, product_quantity: 3, product_price: 18, product_name: 'American BBQ DOG', extra_id: 1, extra_quantity: 3, extra_price: 2, extra_name: 'Mustard (60 g)', }, { orderItemId: 180, product_id: 1, product_quantity: 3, product_price: 18, product_name: 'American BBQ DOG', extra_id: 3, extra_quantity: 3, extra_price: 2, extra_name: 'Roasted onions (30 g)', } ]; function jS(o){ return JSON.stringify(o); } function equals(a,b){ var aa = jS(a); var bb = jS(b); return aa == bb; } function hLen(o){ return Object.keys(o).length; } function hKeys(h){ return Object.keys(h); } function reduce(arr){ var ha=arr[0]; var hb=arr[1]; var hc={}; var xc1={}; //extra 1 when are different var xc2={}; //extra 2 when are different maxhlen = Math.max(hLen(ha),hLen(hb)); akeys = hKeys(ha); bkeys = hKeys(hb); for(i=0;i<maxhlen;i++){ k=akeys[i]; if (ha[k]==hb[k]){ hc[k]=ha[k]; }else{ xc1[k]=ha[k]; xc2[k]=hb[k]; } } hc["extra"]=[xc1,xc2]; return hc; } res=reduce(alist); console.log(res);