CODEWITHSUNDEEP
javascriptjson
user3444463
user3444463

Reputation: 59

JavaScript - How to count each key value in JSON?

JavaScript - How to count each key value in JSON?

[
  {date: "2017-09-28", type: "line", count: 1},
  {date: "2017-09-28", type: "line", count: 1},
  {date: "2017-09-28", type: "dot", count: 1},
  {date: "2017-09-26", type: "dot", count: 1}
]

with this JSON format to:

[
  {date: "2017-09-26", count: 1},
  {date: "2017-09-28", count: 3}
]

or

ultimately, to:

[
  {date: "2017-09-26", dot_count: 1, line_count: 0},
  {date: "2017-09-28", dot_count: 1, line_count: 2}
]

Upvotes: 0

Views: 144

Answers (2)

D Lowther
D Lowther

Reputation: 1619

You are probably looking for array.prototype.reduce.

const test = [
  {date: "2017-09-28", type: "line", count: 1},
  {date: "2017-09-28", type: "line", count: 1},
  {date: "2017-09-28", type: "dot", count: 1},
  {date: "2017-09-26", type: "dot", count: 1}
];
let result = test.reduce((group, current) => {
    let index = group.findIndex(ele => ele.date === current.date);
    if (index === -1) {
        group.push(current);
        return group;
    } 
    group[index].count += current.count;
    return group;
}, []);

for your second level question you probably want to pair array.prototype.map with reduce.

const test = [
      {date: "2017-09-28", type: "line", count: 1},
      {date: "2017-09-28", type: "line", count: 1},
      {date: "2017-09-28", type: "dot", count: 1},
      {date: "2017-09-26", type: "dot", count: 1}
    ];
const mapper = item => ({ 
    date: item.date, 
    dot_count: (item.type === 'dot') ? 1 : 0,
    line_count: (item.type === 'line') ? 1 : 0,
    total_count: item.count,
});
const reducer = (group, current) => {
    let index = group.findIndex(ele => ele.date === current.date);
    if (index === -1) {
        group.push(current);
        return group;
    } 
    group[index] = { 
        ...group[index], 
        dot_count: group[index].dot_count + current.dot_count,
        line_count: group[index].line_count + current.line_count,
        total_count: group[index].total_count + current.total_count,
    };
    return group;
};
let result = test.map(mapper).reduce(reducer, []);
console.log(result);

Upvotes: 0

Nina Scholz
Nina Scholz

Reputation: 386540

You could use a hash table and create a new object if the hash does not exists. Later add the count value to the group.

var data = [{ date: "2017-09-28", type: "line", count: 1 }, { date: "2017-09-28", type: "line", count: 1 }, { date: "2017-09-28", type: "dot", count: 1 }, { date: "2017-09-26", type: "dot", count: 1 }],
    hash = Object.create(null),
    result = [];
    
data.forEach(function (o) {
    if (!hash[o.date]) {
        hash[o.date] = { date: o.date,  dot_count: 0, line_count: 0 };
        result.push(hash[o.date]);
    }
    hash[o.date][o.type + '_count'] += o.count;
});

result.sort(function (a, b) { return a.date.localeCompare(b.date); });

console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 2

Related Questions