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 age which belong to same id which will be as follows

1 = 20
2 = 50
3 = 20
5 = 10

Please find the below code

$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);
}

I don't receive the expected output. the console shows the output as 202020. What has gone wrong in the above code?

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 age which belong to same id which will be as follows

1 = 20
2 = 50
3 = 20
5 = 10

Please find the below code

$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);
}

I don't receive the expected output. the console shows the output as 202020. What has gone wrong in the above code?

• javascript
• arrays

• I've rolled back your edit. Please don't invalidate your question after it has been answered by fixing the code in the question. – Robby Cornelissen Commented Jun 11, 2019 at 3:39

3 Answers 3

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 pact 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).

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);
}

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));