'Sum similar keys in an array of objects
I have an array of objects like the following:
[
{
'name': 'P1',
'value': 150
},
{
'name': 'P1',
'value': 150
},
{
'name': 'P2',
'value': 200
},
{
'name': 'P3',
'value': 450
}
]
I need to add up all the values for objects with the same name. (Probably also other mathematical operations like calculate average.) For the example above the result would be:
[
{
'name': 'P1',
'value': 300
},
{
'name': 'P2',
'value': 200
},
{
'name': 'P3',
'value': 450
}
]
Solution 1:[1]
First iterate through the array and push the 'name' into another object's property. If the property exists add the 'value' to the value of the property otherwise initialize the property to the 'value'. Once you build this object, iterate through the properties and push them to another array.
Here is some code:
var obj = [
{ 'name': 'P1', 'value': 150 },
{ 'name': 'P1', 'value': 150 },
{ 'name': 'P2', 'value': 200 },
{ 'name': 'P3', 'value': 450 }
];
var holder = {};
obj.forEach(function(d) {
if (holder.hasOwnProperty(d.name)) {
holder[d.name] = holder[d.name] + d.value;
} else {
holder[d.name] = d.value;
}
});
var obj2 = [];
for (var prop in holder) {
obj2.push({ name: prop, value: holder[prop] });
}
console.log(obj2);Hope this helps.
Solution 2:[2]
An ES6 approach to group by name:
You can convert your array of objects to a Map by using .reduce(). The Map has key-value pairs, where each key is the name, and each value is the accumulated sum of values for that particular name key. You can then easily convert the Map back into an array using Array.from(), where you can provide a mapping function that will take the keys/values of the Map and convert them into objects:
const arr = [ { 'name': 'P1', 'value': 150 }, { 'name': 'P1', 'value': 150 }, { 'name': 'P2', 'value': 200 }, { 'name': 'P3', 'value': 450 } ];
const res = Array.from(arr.reduce(
(m, {name, value}) => m.set(name, (m.get(name) || 0) + value), new Map
), ([name, value]) => ({name, value}));
console.log(res);Grouping by more than just name:
Here's an approach that should work if you have other overlapping properties other than just name (the keys/values need to be the same in both objects for them to "group"). It involves iterating through your array and reducing it to Map which holds key-value pairs. Each key of the new Map is a string of all the property values you want to group by, and so, if your object key already exists then you know it is a duplicate, which means you can add the object's current value to the stored object. Finally, you can use Array.from() to transform your Map of key-value pairs, to an array of just values:
const arr = [{'name':'P1','value':150},{'name':'P1','value':150},{'name':'P2','value':200},{'name':'P3','value':450}];
const res = Array.from(arr.reduce((acc, {value, ...r}) => {
const key = JSON.stringify(r);
const current = acc.get(key) || {...r, value: 0};
return acc.set(key, {...current, value: current.value + value});
}, new Map).values());
console.log(res);Solution 3:[3]
You can use Array.reduce() to accumulate results during each iteration.
var arr = [{'name':'P1','value':150},{'name':'P1','value':150},{'name':'P2','value':200},{'name':'P3','value':450}];
var result = arr.reduce(function(acc, val){
var o = acc.filter(function(obj){
return obj.name==val.name;
}).pop() || {name:val.name, value:0};
o.value += val.value;
acc.push(o);
return acc;
},[]);
console.log(result);Solution 4:[4]
For some reason when I ran the code by @Vignesh Raja, I obtained the "sum" but also items duplicated. So, I had to remove the duplicates as I described below.
Original array:
arr=[{name: "LINCE-01", y: 70},
{name: "LINCE-01", y: 155},
{name: "LINCE-01", y: 210},
{name: "MIRAFLORES-03", y: 232},
{name: "MIRAFLORES-03", y: 267}]
Using @VigneshRaja's code:
var result = arr.reduce(function(acc, val){
var o = acc.filter(function(obj){
return obj.name==val.name;
}).pop() || {name:val.name, y:0};
o.y += val.y;
acc.push(o);
return acc;
},[]);
console.log(result);
First outcome:
result: [{name: "LINCE-01", y: 435},
{name: "LINCE-01", y: 435},
{name: "LINCE-01", y: 435},
{name: "MIRAFLORES-03", y: 499},
{name: "MIRAFLORES-03", y: 499}]
Removing the duplicates:
var finalresult = result.filter(function(itm, i, a) {
return i == a.indexOf(itm);
});
console.log(finalresult);
Finally, I obtained what I whished:
finalresult = [{name: "LINCE-01", y: 435},
{name: "MIRAFLORES-03", y: 657}]
Regards,
Solution 5:[5]
I have customized Mr Nick Parsons answer(Thanks for the idea). if you need to sum multiple key values.
var arr = [{'name':'P1','value':150,'apple':10},{'name':'P1','value':150,'apple':20},{'name':'P2','value':200,'apple':30},{'name':'P3','value':450,'apple':40}];
var res = Object.values(arr.reduce((acc, {value,apple , ...r}) => {
var key = Object.entries(r).join('-');
acc[key] = (acc[key] || {...r, apple:0,value: 0});
return (acc[key].apple += apple, acc[key].value += value, acc);
}, {}));
console.log(res);
Solution 6:[6]
One more solution which is clean, I guess
var obj = [
{ 'name': 'P1', 'value': 150 },
{ 'name': 'P1', 'value': 150 },
{ 'name': 'P2', 'value': 200 },
{ 'name': 'P3', 'value': 450 }
];
var result = [];
Array.from(new Set(obj.map(x => x.name))).forEach(x => {
result.push(obj.filter(y => y.name === x).reduce((output,item) => {
let val = output[x] === undefined?0:output[x];
output[x] = (item.value + val);
return output;
},{}));
})
console.log(result);if you need to keep the object structure same than,
var obj = [
{ 'name': 'P1', 'value': 150 },
{ 'name': 'P1', 'value': 150 },
{ 'name': 'P2', 'value': 200 },
{ 'name': 'P2', 'value': 1000 },
{ 'name': 'P3', 'value': 450 }
];
let output = [];
let result = {};
let uniqueName = Array.from(new Set(obj.map(x => x.name)));
uniqueName.forEach(n => {
output.push(obj.filter(x => x.name === n).reduce((a, item) => {
let val = a['name'] === undefined? item.value:a['value']+item.value;
return {name:n,value:val};
},{})
);
});
console.log(output);Solution 7:[7]
I see these complicated reduce with Array from and Map and Set - this is far simpler
const summed = arr.reduce((acc, cur) => {
const item = acc.length > 0 && acc.find(({
name
}) => name === cur.name)
if (item) {
item.value += cur.value
} else acc.push({name:cur.name,value:cur.value});
return acc
}, [])
console.log(arr); // not modified
console.log(summed)<script>
const arr = [{
'name': 'P1',
'value': 150
},
{
'name': 'P1',
'value': 150
},
{
'name': 'P2',
'value': 200
},
{
'name': 'P3',
'value': 450
}
]
</script>Solution 8:[8]
(function () {
var arr = [
{'name': 'P1', 'age': 150},
{'name': 'P1', 'age': 150},
{'name': 'P2', 'age': 200},
{'name': 'P3', 'age': 450}
];
var resMap = new Map();
var result = [];
arr.map((x) => {
if (!resMap.has(x.name))
resMap.set(x.name, x.age);
else
resMap.set(x.name, (x.age + resMap.get(x.name)));
})
resMap.forEach((value, key) => {
result.push({
name: key,
age: value
})
})
console.log(result);
})();Solution 9:[9]
let ary = [
{
'key1': 'P1',
'key2': 150
},
{
'key1': 'P1',
'key2': 150
},
{
'key1': 'P2',
'key2': 200
},
{
'key1': 'P3',
'key2': 450
}
]
result array let newAray = []
for (let index = 0; index < ary.length; index++) {
// console.log(ary[index].key1);
for (let index2 = index + 1; index2 < ary.length; index2++) {
if (ary[index2].key1 == ary[index].key1) {
console.log('match');
ary[index].key2 += ary[index2].key2;
newAry = ary.filter( val => val !== ary[index2]);
newAry = ary.filter(function (e) {
return e !== ary[index2];
});
}
}
}
console.log(newAry)
Solution 10:[10]
Here provide more generic version for this question
/**
* @param {(item: T) => string} keyFn
* @param {(itemA: T, itemB: T) => T} mergeFn
* @param {number[]} list
*/
function compress(keyFn, mergeFn, list) {
return Array.from(
list
.reduce((map, item) => {
const key = keyFn(item);
return map.has(key) // if key already existed
? map.set(key, mergeFn(map.get(key), item)) // merge two items together
: map.set(key, item); // save item in map
}, new Map())
.values()
);
}
const testcase = [
{
name: "P1",
value: 150,
},
{
name: "P1",
value: 150,
},
{
name: "P2",
value: 200,
},
{
name: "P3",
value: 450,
},
];
console.log(
compress(
/* user define which is unique key */
({ name }) => name,
/* how to merge two item together */
(a, b) => ({ name: a.name, value: a.value + b.value }),
/* array */
testcase
)
)Solution 11:[11]
The method that Vignesh Raja posted will let you sum various values in an array of objects by the key or other property these method will work better
Solution 12:[12]
let arr = [
{'name':'P1','value':150,'apple':10},
{'name':'P1','value':150,'apple':20},
{'name':'P2','value':200,'apple':30},
{'name':'P2','value':600,'apple':30},
{'name':'P3','value':450,'apple':40}
];
let obj = {}
arr.forEach((item)=>{
if(obj[item.name]){
obj[item.name].value = obj[item.name].value + item.value
}else{
obj[item.name] = item
}
})
let valuesArr = Object.values(obj)
console.log(valuesArr);
Output
[ { name: "P1", value: 300, apple: 10 },
{ name: "P2", value: 800, apple: 30 },
{ name: "P3", value: 450, apple: 40 } ]
Solution 13:[13]
let data= [
{
'key1': 'P1',
'key2': 150
},
{
'key1': 'P1',
'key2': 150
},
{
'key1': 'P2',
'key2': 200
},
{
'key1': 'P3',
'key2': 450
}
]
var holder = []
data.forEach( index => {
const data = holder.find( i => i.key1=== index.key1)
if(!data){
holder.push({key1:index.key1,key2:index.key2})
}else{
data.key2 = parseInt(data.key2) + parseInt(index.key2)
}
});
console.log(holder);Sources
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Source: Stack Overflow