使用对象的两个属性减少单个对象数组

Question

I have a single array of objects and I would like to reduce it down to another array of objects based on two keys value pairs.

const original =
    [
        {
            key1: 'a',
            key2: 'AA',
            value: 1
        },
        {
            key1: 'a',
            key2: 'AA',
            anotherValue: 2
        },
        {
            key1: 'b',
            key2: 'BB',
            value: 1
        },
        {
            key1: 'a',
            key2: 'AA',
            yetAnother: 3
        },
        {
            key1: 'b',
            key2: 'BB',
            anotherValue: 4
        },
        {
            key1: 'c',
            key2: 'CC',
            value: 1
        }
    ];

Should be transformed into:

const result =
    [
        {
            key1: 'a',
            key2: 'AA',
            value: 1,
            anotherValue: 2,
            yetAnother: 3
        },
        {
            key1: 'b',
            key2: 'BB',
            value: 1,
            anotherValue: 4
        },
        {
            key1: 'c',
            key2: 'CC',
            value: 1
        },
    ];

Tired using map and reduce and even lodash. However, all my attempts were futile.

Answer 1

Using Array.reduce , you can group the objects by key1 and key2 value pairs. And the variable groupBy object values contain the result you want and you can generate the values only using Object.values(groupBy) .

 const original = [ { key1: 'a', key2: 'AA', value: 1 }, { key1: 'a', key2: 'AA', anotherValue: 2 }, { key1: 'b', key2: 'BB', value: 1 }, { key1: 'a', key2: 'AA', yetAnother: 3 }, { key1: 'b', key2: 'BB', anotherValue: 4 }, { key1: 'c', key2: 'CC', value: 1 } ]; const groupBy = original.reduce((acc, cur) => { const { key1, key2, ...rest } = cur; const key = key1 + "_" + key2; acc[key] ? acc[key] = { ...acc[key], ...rest } : acc[key] = cur; return acc; }, {}); const result = Object.values(groupBy); console.log(result);

Answer 2

Using Array.prototype.reduce() , build up a Map of entries, keyed by the combination of any key* properties while merging in the other properties.

Then you can convert the Map values into a new array

 const original = [{"key1":"a","key2":"AA","value":1},{"key1":"a","key2":"AA","anotherValue":2},{"key1":"b","key2":"BB","value":1},{"key1":"a","key2":"AA","yetAnother":3},{"key1":"b","key2":"BB","anotherValue":4},{"key1":"c","key2":"CC","value":1}] const t1 = performance.now() const result = [...original.reduce((map, obj) => { // create a key from all the "key*" properties const key = Object.keys(obj) .filter(key => key.startsWith("key")) .sort() .map(key => obj[key]).join(":") // looks like "a:AA", "b:BB", etc // merge with previously found matches const entry = { ...(map.get(key) ?? {}), ...obj } // collect the merged object return map.set(key, entry) }, new Map()).values()] const t2 = performance.now() console.info(result, `in ${t2 - t1}ms`)

 .as-console-wrapper { max-height: 100% !important; }