Retrieve every item from a collection

Question

Retrieve every item from a collection

Here's what I've got:

objArray1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}];

objArray2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }];

I'm using Javascript to create an array with all the candidates and display the number of votes each one has. Calculating the votes is simple, but combining all the candidates into one array is where I need help.

The final array should include: Alex, Paul, Ben, and Melisa.

Your assistance would be greatly appreciated!

javascript arrays arraylist

Answer 1

Answer №1

To efficiently group data by name, consider using a hashtable.

var array1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}],
    array2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }],
    grouped = [array1, array2].reduce(function (hash) {
        return function (r, a) {
            a.forEach(function (o, i) {
                var name = o['candidate' + (i + 1)];
                if (!hash[name]) {
                    hash[name] = { candidate: name, votes: 0 };
                    r.push(hash[name]);
                }
                hash[name].votes += o.votes;
            });
            return r;
        };
    }(Object.create(null)), []);
    
console.log(grouped);

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Answer 2

To efficiently group data by name, consider using a hashtable.

var array1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}],
    array2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }],
    grouped = [array1, array2].reduce(function (hash) {
        return function (r, a) {
            a.forEach(function (o, i) {
                var name = o['candidate' + (i + 1)];
                if (!hash[name]) {
                    hash[name] = { candidate: name, votes: 0 };
                    r.push(hash[name]);
                }
                hash[name].votes += o.votes;
            });
            return r;
        };
    }(Object.create(null)), []);
    
console.log(grouped);

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Answer 3

Answer №2

let contestants = [];
let tally = 0;
for(let x=0;objArray2.length>x;x++){
    tally = 0;
    //include votes in contestant array
    for(let y=0;contestants.length>y;y++){
        if(contestants[y].title==objArray2[x][Object.keys(objArray2[x])[0]]){
           contestants[y].points = contestants[y].points+objArray2[x].points;
           tally = 1;
        }
    }
    //if contender not present in toting array, create new one
    if(tally==0){
         let temp = {};
         temp.title = objArray2[x].title;
         temp.points = objArray2[x].points;
         //append to the array
         contestants.push(temp);
    }
}

console.log(contestants);

Answer 4

let contestants = [];
let tally = 0;
for(let x=0;objArray2.length>x;x++){
    tally = 0;
    //include votes in contestant array
    for(let y=0;contestants.length>y;y++){
        if(contestants[y].title==objArray2[x][Object.keys(objArray2[x])[0]]){
           contestants[y].points = contestants[y].points+objArray2[x].points;
           tally = 1;
        }
    }
    //if contender not present in toting array, create new one
    if(tally==0){
         let temp = {};
         temp.title = objArray2[x].title;
         temp.points = objArray2[x].points;
         //append to the array
         contestants.push(temp);
    }
}

console.log(contestants);

Answer 5

Answer №3

Develop a function that creates an object with the candidate name as the key and their total vote count as the value.

var objArray1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}], objArray2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }];

var result = []
  // combine two arrays
  .concat(objArray1, objArray2)
  // iterate over the arrays
  .reduce(function(object, item) {
    // get the key excluding votes
    var key = Object.keys(item).find(function(k) {
      return k !== 'votes';
    })
    // define property if not already defined
    object[key] = object[key] || 0;
    // add the vote count
    object[key] += item.votes;
    // return object reference
    return object;
    // set initial value as empty object
  }, {});

console.log(result);
// get the names array if needed
console.log(Object.keys(result));

Answer 6

Develop a function that creates an object with the candidate name as the key and their total vote count as the value.

var objArray1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}], objArray2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }];

var result = []
  // combine two arrays
  .concat(objArray1, objArray2)
  // iterate over the arrays
  .reduce(function(object, item) {
    // get the key excluding votes
    var key = Object.keys(item).find(function(k) {
      return k !== 'votes';
    })
    // define property if not already defined
    object[key] = object[key] || 0;
    // add the vote count
    object[key] += item.votes;
    // return object reference
    return object;
    // set initial value as empty object
  }, {});

console.log(result);
// get the names array if needed
console.log(Object.keys(result));

Answer 7

Answer №4

Here is a concise solution that utilizes Array.prototype.concat(), Array.prototype.reduce(), and Array.prototype.map() functions:

var candidatesSet1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}],
    candidatesSet2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }],
    
    groupedCandidates = candidatesSet1.concat(candidatesSet2).reduce(function(result, object){
        var key = Object.keys(object).filter(function(key){
                return key.indexOf('candidate') === 0; 
            })[0];

        (result[object[key]])? result[object[key]].votes += object.votes : result[object[key]] = {candidate: object[key], votes: object.votes};
        return result;
    }, {}),

    finalResult = Object.keys(groupedCandidates).map(function(k){ return groupedCandidates[k]; });
    
console.log(finalResult);

Answer 8

Here is a concise solution that utilizes Array.prototype.concat(), Array.prototype.reduce(), and Array.prototype.map() functions:

var candidatesSet1 = [ { candidate1: "Alex" , votes: 4}, { candidate2: "Paul", votes: 3}],
    candidatesSet2 = [ { candidate1: "Alex" , votes: 7}, { candidate2: "Ben", votes: 3}, { candidate3: "Melisa", votes:8 }],
    
    groupedCandidates = candidatesSet1.concat(candidatesSet2).reduce(function(result, object){
        var key = Object.keys(object).filter(function(key){
                return key.indexOf('candidate') === 0; 
            })[0];

        (result[object[key]])? result[object[key]].votes += object.votes : result[object[key]] = {candidate: object[key], votes: object.votes};
        return result;
    }, {}),

    finalResult = Object.keys(groupedCandidates).map(function(k){ return groupedCandidates[k]; });
    
console.log(finalResult);

Answer 9

Answer №5

To obtain the requested list of names

let combinedArrays = objArray1.concat(objArray2);
let CandidatesList = [];
let temp = [];

for (let i in combinedArrays) {
    temp[combinedArrays[i][Object.keys(combinedArrays[i])[0]]] = 1;
}
CandidatesList = Object.keys(temp);

To generate an array with candidates and total votes

let combinedArrays = objArray1.concat(objArray2);
let CandidatesList = [];

for (let i in combinedArrays) {
    let name = combinedArrays[i][Object.keys(combinedArrays[i])[0]];
    if (CandidatesList[name]) {
        CandidatesList[name] += combinedArrays[i].votes;
    } else {
        CandidatesList[name] = combinedArrays[i].votes;
    }
}

Answer 10

To obtain the requested list of names

let combinedArrays = objArray1.concat(objArray2);
let CandidatesList = [];
let temp = [];

for (let i in combinedArrays) {
    temp[combinedArrays[i][Object.keys(combinedArrays[i])[0]]] = 1;
}
CandidatesList = Object.keys(temp);

To generate an array with candidates and total votes

let combinedArrays = objArray1.concat(objArray2);
let CandidatesList = [];

for (let i in combinedArrays) {
    let name = combinedArrays[i][Object.keys(combinedArrays[i])[0]];
    if (CandidatesList[name]) {
        CandidatesList[name] += combinedArrays[i].votes;
    } else {
        CandidatesList[name] = combinedArrays[i].votes;
    }
}

Retrieve every item from a collection

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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