Merge 2 objects in an array where the values are an array

Question

I am trying to merge values in 2 objects from the same array. The objects in this case are similar and the values I want to merge are arrays(Set)

var array = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ];

Expected Output

[ { name: "foo1", value: ["val1","val2", "val3"] },{ name: "foo2", value: ["val4","val4", "val5"] } ]

My Code

var output = []; array.forEach(function(item) { var existing = output.filter(function(v, i) { return v.name == item.name; }); if (existing.length) { var existingIndex = output.indexOf(existing[0]); let newValue = new Set(output[existingIndex].value).add(item.value) output[existingIndex].value = Array.from(newValue); } else { output.push(item); } });

Output Gotten

[ { name: "foo1", value: ["val1", "val2", ["val2", "val3"]] }, { name: "foo2", value: ["val4", ["val4", "val5"]] }]

How can I get the expected output (ES6 would also be preferred)

The expected output should be value: ["val4", "val5"] instead of value: ["val4","val4", "val5"], is that right? — Md Sabbir Alam
– Md Sabbir Alam, Commented Jan 7, 2021 at 10:31

Naren · Accepted Answer · 2021-01-07 10:22:37Z

Try this

const array = [ { "name": "foo1", "value": [ "val1", "val2", "val3" ] }, { "name": "foo1", "value": [ "val2", "val3" ] }, { "name": "foo2", "value": [ "val4", "val5" ] }, { "name": "foo2", "value": [ "val4", "val5" ] } ] const result = [] for (const item of array) { const existingItem = result.find(i => i.name === item.name) if (existingItem) { existingItem.value = [...new Set([...existingItem.value, ...item.value])] } else { result.push(item) } } console.log(result)

gscHeartA · Accepted Answer · 2021-01-07 10:22:39Z

Is this code solve your problem?

var array = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; var output = []; array.forEach(function(item) { var existing = output.filter(function(v, i) { return v.name == item.name; }); if (existing.length) { var existingIndex = output.indexOf(existing[0]); let newValue = new Set(output[existingIndex].value.concat(item.value)) output[existingIndex].value = Array.from(newValue); } else { output.push(item); } });

Kartik Narang · Accepted Answer · 2021-01-07 10:28:33Z

try

var arr = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; var arr2={} arr.map((elem,ind)=>{ if(!arr2[elem.name]){ arr2[elem.name]=[] } arr2[elem.name]=[...arr2[elem.name],...elem.value] }) arr=Object.keys(arr2); arr.map((elem,ind)=>{ arr[ind]={name:elem,value:arr2[elem]}; })

Md Sabbir Alam · Accepted Answer · 2021-01-07 10:30:42Z

You can do the following using reduce,

var array = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; res = array.reduce((prev, curr) => { let index = prev.findIndex(item => item.name === curr.name); if(index > -1) { s = new Set([...prev[index].value, ...curr.value]); prev[index].value = Array.from(s); } else { prev.push(curr); } return prev; },[]); console.log(res);

Nenad Vracar · Accepted Answer · 2021-01-07 10:35:50Z

You could use reduce method with a Map as accumulator value and then use spread syntax ... on Map values to get an array of values.

var array = [{"name":"foo1","value":["val1","val2","val2","val3"]},{"name":"foo1","value":["val2","val3"]},{"name":"foo2","value":["val4","val4","val5"]},{"name":"foo2","value":["val4","val5"]}] const map = array.reduce((r, { name, value }) => { if (!r.has(name)) r.set(name, { name, value }) else r.get(name).value.push(...value) r.get(name).value = [...new Set(r.get(name).value)] return r; }, new Map) const result = [...map.values()] console.log(result)

Thomas Sablik · Accepted Answer · 2021-01-07 11:06:19Z

One approach is to create an unique list of keys and iterate over it. Create an array for each key and merge the values. The vanilla js way is:

Array.from(new Set(array.map(el => el.name))) .map(name => ({ name, value: Array.from(new Set(array.filter(el => el.name === name).flatMap(el => el.value))) }))

Example:

const array = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; console.log(Array.from(new Set(array.map(el => el.name))) .map(name => ({ name, value: Array.from(new Set(array.filter(el => el.name === name).flatMap(el => el.value))) })));

Using lodash you can reduce it to

_.uniq(array.map(el => el.name)) .map(name => ({ name, value: _.uniq(array.filter(el => el.name === name).flatMap(el => el.value)) }))

Example:

const array = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; console.log(_.uniq(array.map(el => el.name)) .map(name => ({ name, value: _.uniq(array.filter(el => el.name === name).flatMap(el => el.value)) })));

<script src="https://cdn.jsdelivr.net/npm/[email protected]/lodash.min.js"></script>

Arpan · Accepted Answer · 2021-01-07 19:38:42Z

Find unique values of keys. Match this keys within array and return unique objects. Push this objects in an empty array. Then match other objects value with the new arrays objects value and push the unmatched values to this new array.

var arr = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; let key = []; arr.map((val)=>key.push(val.name)); let uniquekeys = [...new Set(key)]; //unique values of keys let newarr = []; uniquekeys.map((uniquekey,ind)=>{ let reduceunique = arr.filter((vals)=>uniquekey == vals.name); // return matching objects as array newarr.push(reduceunique[0]); // Push unique objects in an empty array for(let i = 1; i<uniquekeys.length;i++){ reduceunique[i].value.map((val)=>{ let existvalue = newarr[ind].value.indexOf(val); // Match every value with the unique objects values if(existvalue<0){ newarr[ind].value.push(val); // push the unmatched value in the array } }); }; }); console.log(newarr);

Molham Al Nasr · Accepted Answer · 2021-01-07 10:31:55Z

try to use Array.reduce and Array.filter to get the result like the following

var array = [ { name: "foo1", value: ["val1","val2"] }, { name: "foo1", value: ["val2", "val3"] }, { name: "foo2", value: ["val4"] }, { name: "foo2", value: ["val4","val5"] }, ]; res = array.reduce((prev, curr) => { let index = prev.findIndex(item => item.name === curr.name); if(index > -1) { prev[index].value = [...prev[index].value, ...curr.value]; prev[index].value = prev[index].value.filter((v,i) => prev[index].value.indexOf(v) === i) } else { prev.push(curr); } return prev; },[]); console.log(res);

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