Sum Values Of Same Id In A Json Array Using Js

I have a json array with Id and age as follows var arrayVal = [{id:'1', age: 20},{id:'2', age: 30},{id:'2', age: '20'},{id:'3', age: 20},{id:'5', age: 10}]; I want to get sum of a

Solution 1:

With a simple reduce() operation:

const array = [{id:"1", age: 20},{id:"2", age: 30},{id:"2", age: "20"},{id:"3", age: 20},{id:"5", age: 10}];

const ages = array.reduce((a, {id, age}) => (a[id] = (a[id] || 0) + +age, a), {});

console.log(ages);

---

Besides the reduce solution being more compact and declarative, the main problem with the code provided is due to coercion. One of the age values has the string "20", forcing the subsequent + operations to be interpreted as string concatenation.

This answer avoids this unexpected side-effect using the +age, forcing age to be a Number (this could be made explicit by doing Number(age) instead).

Solution 2:

The age must be number. It should not be as a string. In your code, id:2 has 20 as string. Kindly check with datatype in arrayVal.

var arrayVal = [{id:"1", age: 20},{id:"2", age: 30},{id:"2", age: 20},{id:"3", age: 20},{id:"5", age: 10}];

$scope.TestFunc = function()
{
var tot = 0;
var arrayVal = [{id:"1", age: 20},{id:"2", age: 30},{id:"2", age: 20},{id:"3", age: 20},{id:"5", age: 10}];
for(var i=0; i <arrayVal.length; i++ )
{
  for(var j=1; j<arrayVal.length - i; j++ )
  {
    if(arrayVal[i].id == arrayVal[j].id)
    {
      tot = arrayVal[i].age.valueOf() + arrayVal[j].age.valueOf();
    }
    else{
      tot = tot + arrayVal[i].age;
    }
  }
}
console.log("-----total----"+tot);
}

Solution 3:

I've prepared another answer using Array#reduce method which returns array of objects instead of simple array:

const arrayVal = [{id:"1", age: 20},{id:"2", age: 30},{id:"2", age: "20"},{id:"3", age: 20},{id:"5", age: 10}];

let summedAges = arrayVal.reduce((a, c) => {
	let filtered = a.filter(el => el.id === c.id);
	if(filtered.length > 0){
		a[a.indexOf(filtered[0])].age += +c.age;
	}else{
		a.push(c);
	}
	return a;
}, []);

console.log(JSON.stringify(summedAges));