Group by date and receive total records of each date and assemble another matrix

Question

[ 
    { data: "23-04", xxx: "xxx, yyy: "yyy },
    { data: "23-04", xxx: "xxx, yyy: "yyy },
    { data: "23-04", xxx: "xxx, yyy: "yyy },
    { data: "23-05", xxx: "xxx, yyy: "yyy },
    { data: "23-05", xxx: "xxx, yyy: "yyy },
    { data: "23-05", xxx: "xxx, yyy: "yyy },
    { data: "23-06", xxx: "xxx, yyy: "yyy },
    { data: "23-06", xxx: "xxx, yyy: "yyy },
    { data: "23-06", xxx: "xxx, yyy: "yyy },
    { data: "23-06", xxx: "xxx, yyy: "yyy },
    { data: "23-06", xxx: "xxx, yyy: "yyy },

]

Hello, I need to take the above array of the total record of each date and create another array of objects containing its own name and total as new key values for example:

[{
        "a": "23-04",
        "b": 3
    }, {
        "a": "23-05",
        "b": 3
    },
    {
        "a": "23-06",
        "b": 5
    }
]

Can be with es6, map, reduce or even with lodash/undescore

I thank anyone who can chew this because I’m three days old and it doesn’t come out the way I need it

Answer 1

Two examples that seem to work...

var origem = [
    { data: "23-04", xxx: "xxx", yyy: "yyy" },
    { data: "23-04", xxx: "xxx", yyy: "yyy" },
    { data: "23-04", xxx: "xxx", yyy: "yyy" },
    { data: "23-05", xxx: "xxx", yyy: "yyy" },
    { data: "23-05", xxx: "xxx", yyy: "yyy" },
    { data: "23-05", xxx: "xxx", yyy: "yyy" },
    { data: "23-06", xxx: "xxx", yyy: "yyy" },
    { data: "23-06", xxx: "xxx", yyy: "yyy" },
    { data: "23-06", xxx: "xxx", yyy: "yyy" },
    { data: "23-06", xxx: "xxx", yyy: "yyy" },
    { data: "23-06", xxx: "xxx", yyy: "yyy" },
];

var result1 = Object.entries(origem.reduce((acc, o) => (acc[o.data] = (acc[o.data] || 0) + 1, acc), {}))
    .map(([a, b]) => ({ a, b }));


let counts = {};
origem.forEach(el => counts[el.data] = (counts[el.data] || 0) + 1);
var result2 = Object.entries(counts).map(([a, b]) => ({ a, b }));

console.log(result1);
console.log(result2);