How to dynamically calculate the fields in array of objects for a particular name filed in JavaScript

Question

My code works fine to calculate various perks for towns. But I want to dynamically calculate other fields values as well.

var obj = [{
  "Town": "Newton",
  "PropertyType": "Multi Family",
  "InvestmentType": "Homeownership",
  "Perks": "Retail Store"
}, {
  "Town": "South Surrey",
  "PropertyType": "Multi Family",
  "InvestmentType": "Investment Property",
  "Perks": "Retail Store"
}, {
  "Town": "South Surrey",
  "PropertyType": "Multi Family",
  "InvestmentType": "Investment Property",
  "Perks": "Bus Station"
}, {
  "Town": "South Surrey",
  "PropertyType": "Condo",
  "InvestmentType": "Homeownership",
  "Perks": "Retail Store"
}];

var result = Object.values(obj.reduce(
  (a, { Town, Perks }) => { a[Town] = a[Town] || { Town, perks: {} };
  a[Town].perks[Perks] = (a[Town].perks[Perks] || 0) + 1;
  return a;
}, {}));

console.log(result);

question from:https://stackoverflow.com/questions/65862050/how-to-dynamically-calculate-the-fields-in-array-of-objects-for-a-particular-nam

Answer 1

On each iteration destructure the object, and get the Town, and the rest of properties. Get the entries of the other properties, and iterate it with Array.forEach(). As you did for Town create the object for the property key and value as needed, and increment the count.

const obj=[{"Town":"Newton","PropertyType":"Multi Family","InvestmentType":"Homeownership","Perks":"Retail Store"}, {"Town":"South Surrey","PropertyType":"Multi Family","InvestmentType":"Investment Property","Perks":"Retail Store"}, {"Town":"South Surrey","PropertyType":"Multi Family","InvestmentType":"Investment Property","Perks":"Bus Station"}, {"Town":"South Surrey","PropertyType":"Condo","InvestmentType":"Homeownership","Perks":"Retail Store"}];

const result = Object.values(obj.reduce((a, { Town, ...rest }) => {
  a[Town] = a[Town] || { Town };
  
  Object.entries(rest)
    .forEach(([k, v]) => {
      a[Town][k] = a[Town][k] || {};
      
      a[Town][k][v] = (a[Town][k][v] || 0) + 1;
    });
  
  return a;
}, {}));

console.log(result);