Extracting object properties and tallying their occurrences

Question

Extracting object properties and tallying their occurrences

How can I extract a single property from an array of objects like the following:

[{"name":"Bryan","id":016, "counter":0}, {"name":"John","id":04, "counter":2}, {"name":"Alicia","id":07, "counter":6}, {"name":"Jenny","id":015, "counter":9}, {"name":"Bryan","id":016, "counter":0}, {"name":"Jenny","id":015, "counter":9}, {"name":"John","id":04, "counter":2}, {"name":"Jenny"    ,"id":015, "counter":9}];

I want to extract the name property from each object and then count the number of occurrences of each name to create the following structure:

[{"name":"Bryan","Number":2},
{"name":"John","Number":2},
{"name":"Alicia","Number":1},
{"name":"Jenny","Number":3}]

javascript arrays json object

Answer 1

Answer №1

Are you interested in disregarding the existing id and counter props?

One approach could be to create an object to maintain unique names and then convert it back to an array:

var data = [{"name": "Bryan",  "id": 016,  "counter": 0}, {  "name": "John",  "id": 04,  "counter": 2}, {  "name": "Alicia",  "id": 07,  "counter": 6}, {  "name": "Jenny",  "id": 015,  "counter": 9}, {  "name": "Bryan",  "id": 016,  "counter ": 0}, {  "name": "Jenny",  "id": 015,  "counter ": 9}, {  "name": "John",  "id": 04,  "counter": 2}, {  "name": "Jenny",  "id": 015,  "counter": 9}];

var result = data.reduce(function(result, item) {
  if (!result[item.name]) {
    result[item.name] = {
      name: item.name,
      counter: 0
    };
  }

  result[item.name].counter += 1;
  
  return result;
}, {});

console.log(Object.keys(result).map(function(key) { return result[key] }));

Answer 2

Are you interested in disregarding the existing id and counter props?

One approach could be to create an object to maintain unique names and then convert it back to an array:

var data = [{"name": "Bryan",  "id": 016,  "counter": 0}, {  "name": "John",  "id": 04,  "counter": 2}, {  "name": "Alicia",  "id": 07,  "counter": 6}, {  "name": "Jenny",  "id": 015,  "counter": 9}, {  "name": "Bryan",  "id": 016,  "counter ": 0}, {  "name": "Jenny",  "id": 015,  "counter ": 9}, {  "name": "John",  "id": 04,  "counter": 2}, {  "name": "Jenny",  "id": 015,  "counter": 9}];

var result = data.reduce(function(result, item) {
  if (!result[item.name]) {
    result[item.name] = {
      name: item.name,
      counter: 0
    };
  }

  result[item.name].counter += 1;
  
  return result;
}, {});

console.log(Object.keys(result).map(function(key) { return result[key] }));

Answer 3

Answer №2

To keep track of the number of occurrences of each name, a hash table can be utilized as a reference.

var data = [{ name: "Bryan", id: "016", count: 0 }, { name: "John", id: "04", count: 2 }, { name: "Alicia", id: "07", count: 6 }, { name: "Jenny", id: "015", count: 9 }, { name: "Bryan", id: "016", count: 0 }, { name: "Jenny", id: "015", count: 9 }, { name: "John", id: "04", count: 2 }, { name: "Jenny", id: "015", count: 9 }], grouped = [];

data.forEach(function (item) {
    if (!this[item.name]) {
        this[item.name] = { name: item.name, occurrences: 0 };
        grouped.push(this[item.name]);
    }
    this[item.name].occurrences++;
}, Object.create(null));

console.log(grouped);

Answer 4

To keep track of the number of occurrences of each name, a hash table can be utilized as a reference.

var data = [{ name: "Bryan", id: "016", count: 0 }, { name: "John", id: "04", count: 2 }, { name: "Alicia", id: "07", count: 6 }, { name: "Jenny", id: "015", count: 9 }, { name: "Bryan", id: "016", count: 0 }, { name: "Jenny", id: "015", count: 9 }, { name: "John", id: "04", count: 2 }, { name: "Jenny", id: "015", count: 9 }], grouped = [];

data.forEach(function (item) {
    if (!this[item.name]) {
        this[item.name] = { name: item.name, occurrences: 0 };
        grouped.push(this[item.name]);
    }
    this[item.name].occurrences++;
}, Object.create(null));

console.log(grouped);

Answer 5

Answer №3

Let's give this a go. We start by creating a dictionary called nameDict to store names and their respective counts. Next, we iterate through a list of names to tally them up.

var arr = [{"name":"Bryan","id":"016", "counter":0}, {"name":"John","id":"04", "counter":2}, {"name":"Alicia","id":"07", "counter":6}, {"name":"Jenny","id":"015", "counter":9}, {"name":"Bryan","id":"016", "counter":0}, {"name":"Jenny","id":"015", "counter":9}, {"name":"John","id":"04", "counter":2}, {"name":"Jenny","id":"015", "counter":9}];
var nameDict = {};

for(var i = 0; i < arr.length; i++)
{
    var name = arr[i].name;
    if(nameDict[name] == undefined){
        //if the name is not in the dictionary, add it with a count of 1
        nameDict[name] = 1
    } else {
        //if the name is already in the dictionary, increment the count
        nameDict[name] += 1
    }
}

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

Answer 6

Let's give this a go. We start by creating a dictionary called nameDict to store names and their respective counts. Next, we iterate through a list of names to tally them up.

var arr = [{"name":"Bryan","id":"016", "counter":0}, {"name":"John","id":"04", "counter":2}, {"name":"Alicia","id":"07", "counter":6}, {"name":"Jenny","id":"015", "counter":9}, {"name":"Bryan","id":"016", "counter":0}, {"name":"Jenny","id":"015", "counter":9}, {"name":"John","id":"04", "counter":2}, {"name":"Jenny","id":"015", "counter":9}];
var nameDict = {};

for(var i = 0; i < arr.length; i++)
{
    var name = arr[i].name;
    if(nameDict[name] == undefined){
        //if the name is not in the dictionary, add it with a count of 1
        nameDict[name] = 1
    } else {
        //if the name is already in the dictionary, increment the count
        nameDict[name] += 1
    }
}

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

Extracting object properties and tallying their occurrences

Answer №1

Answer №2

Answer №3

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