Pivot or Transforming JavaScript object

Question

I have the following JavaScript object. I need to generate a new object from the given object. What is the approach I should take in JavaScript?

[
 {\"name\"         


        

Answer 1

The below code will work for your requirement. The final result is stored in the variable result which holds the array object.

    var source = [{
            "name": "Dan",
            "city": "Columbus",
            "ZIP": "47201"
        },
        {
            "name": "Mark",
            "city": "Tampa",
            "ZIP": "33602"
        },
        {
            "name": "Jen",
            "city": "Columbus",
            "ZIP": "47201"
        }
    ];

    var result = [];
    finalarr('ZIP');

    function finalarr(propname) {
        var obj = JSON.parse(JSON.stringify(source));

        obj.forEach(function(elm,i) {
            var arr = {};var chli=[];var charr={};
            var flag = 0;

            for (var prop in elm) {
                if(prop != propname){
                    charr[prop]=elm[prop];
                }
            }

            for(var i=0;i<result.length;i++){
                if(result[i][elm[propname]]){
                    result[0][elm[propname]].push(charr);
                    //console.log(result[i][propname]);
                    flag = 1;
                }
            }

            if(flag == 0){
                chli.push(charr);
                arr["count"] = checkarr(obj,propname,elm[propname]);        
                arr[elm[propname]]=chli;
                result.push(arr);
            }
        });
    }

    function checkarr(obj,propname,value){
        var count = 0;
        obj.forEach(function(elm,i) {
            if(elm[propname] == value){
                count++;
            }
        });

        return count;
    }

console.log(result);

Answer 2

I don't know why you want the .count property, when that can be accessed via the array's .length property, but anyway:

const input = [
  {"name": "Dan",  "city" : "Columbus", "ZIP":"47201"},
  {"name": "Jen",  "city" : "Columbus", "ZIP":"47201"},
  {"name": "Mark", "city" : "Tampa",  "ZIP":"33602"},
]

const working = input.reduce((acc, {ZIP, name, city}) => {
  (acc[ZIP] || (acc[ZIP] = [])).push({name, city})
  return acc
}, {})

const output = Object.keys(working)
  .map(k => ({[k]: working[k], count: working[k].length}))

console.log(output)

Further reading:

• Array .reduce()
• Array .map()
• Object.keys()
• Unpacking fields from objects passed as function parameters
• Computed property names