Syntax error Calculate average from JSON data based on multiple filters JavaScript

Calculate average from JSON data based on multiple filters JavaScript

Suppose, we have an array of objects like this −

const arr = [
   { "SupplierName" : "John", "Category " : "A", "Points" : 3 },
   { "SupplierName" : "John", "Category " : "A", "Points" : 11 },
   { "SupplierName" : "John", "Category " : "A", "Points" : undefined },
   { "SupplierName" : "John", "Category " : "B", "Points" : 2 },
   { "SupplierName" : "John", "Category " : "B", "Points" : 6 },
   { "SupplierName" : "Praveen", "Category " : "A", "Points" : 3 },
   { "SupplierName" : "Praveen", "Category " : "A", "Points" : 7 }
];

We are required to write a JavaScript function that takes in one such array.

The function should do the following things −

  • Group repeating suppliers into one unique separate object (by repeating, we mean objects with same "SupplierName" and "Category" field).
  • Add up their points together
  • Add a new "average field to each object, containing the average points of that supplier.

So, finally the output should look like −

const output = [
   { "SupplierName" : "John", "Category " : "A", "Points" : 14, "Average" : 7 },
   { "SupplierName" : "John", "Category " : "B", "Points" : 8, "Average" : 4 },
   { "SupplierName" : "Praveen", "Category " : "A", "Points" : 10, "Average" : 5 }
];

Example

const arr = [
   { "SupplierName" : "John", "Category " : "A", "Points" : 3 },
   { "SupplierName" : "John", "Category " : "A", "Points" : 11 },
   { "SupplierName" : "John", "Category " : "A", "Points" : undefined },
   { "SupplierName" : "John", "Category " : "B", "Points" : 2 },
   { "SupplierName" : "John", "Category " : "B", "Points" : 6 },
   { "SupplierName" : "Praveen", "Category " : "A", "Points" : 3 },
   { "SupplierName" : "Praveen", "Category " : "A", "Points" : 7 }
];
const groupAndAverage = (arr = []) => {
   const groups = arr.reduce((acc, obj) => {
       const name = obj.SupplierName + obj.Category;
      if (acc[name]) {
         if (obj.Points) (acc[name].Points += obj.Points) && ++acc[name].Average;
      }
      else { acc[name] = obj;
         acc[name].Average = 1;
         // taking 'Average' attribute as an items counter(on the first phase)
      };
      return acc;
   }, {});
   // getting "average of Points" const res = Object.keys(groups).map( name => {       groups[name].Average = Math.round(groups[name].Points/groups[name].Average);
      return groups[name];
   });
   return res;
}; console.log(JSON.stringify(groupAndAverage(arr), undefined, 4));

Output

And the output in the console will be −

[
   {
      "SupplierName": "John",
      "Category ": "A",
      "Points": 22,
      "Average": 6
   },
   {
      "SupplierName": "Praveen",
      "Category ": "A",
      "Points": 10,
      "Average": 5
   }
]
Updated on: 2020-11-23T07:05:38+05:30

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