Find Unique Values in Array datawise

Question

I've an array which contains the data of users joined in last seven days from current date. eg users=['19 Dec', '21 Dec', '21 Dec'] In this array, three users joined in last 7 days. I'm trying to find the unique occurence with this function. `

 let occurences = users.reduce(function (acc, curr) {
              return acc[curr] ? ++acc[curr] : (acc[curr] = 1), acc;
            }, {});

`

It's returning the object that contains the following key-pairs: {19 Dec: 1, 21 Dec: 2} I'm expecting to fill the missing values in the object with 0 and with it's respective date. So, the final O/P will be: {19 Dec: 1, 20 Dec: 0, 21 Dec: 2, 22 Dec: 0, 23 Dec: 0, 24 Dec: 0, 25 Dec: 0}

Can someone please help me out to solve this?

I'm expecting to fill the missing values in the object with 0 and with it's respective date. So, the final O/P will be: {19 Dec: 1, 20 Dec: 0, 21 Dec: 2, 22 Dec: 0, 23 Dec: 0, 24 Dec: 0, 25 Dec: 0}

Answer 1

Perhaps something like this will work for you. I'm using a modified version of the code found in this SO answer . The formatting was done thanks to this SO answer .

First, let's build an array containing the last 7 days.

Date.prototype.addDays = function(days) {
    var date = new Date(this.valueOf());
    date.setDate(date.getDate() + days);
    return date;
}

function getDates(startDate, stopDate) {
    var dateArray = [];
    var currentDate = startDate;
    while (currentDate <= stopDate) {
        var calendarDay = currentDate.getDate();
        var monthName = new Intl.DateTimeFormat('en-US', options).format(currentDate);
        dateArray.push(calendarDay + " " + monthName);
        currentDate = currentDate.addDays(1);
    }
    return dateArray;
}

var options = { month: 'short' };
var end = new Date();
var start = end.addDays(-7);

var dateArray = getDates(start,end);

Next, let's assume that this is your JSON object with date - short month names as keys, and number of non-zero users as values.

let occurences = {
    "19 Dec": 1,
    "21 Dec": 2
};

We'll make a working copy of it, which we'll then modify as needed. You don't have to do this - you can declare occurences differently, and modify it instead, but I'm doing it with the copy.

var copyOcc = occurences;

Next, we'll loop through our dateArray , and check if there's a key in occurences corresponding to the current value from dateArray .

for(var i = 0; i < dateArray.length; i++) {
    // If the key isn't there, add it
    if(!copyOcc.hasOwnProperty(dateArray[i])) {
        copyOcc[dateArray[i]] = 0;
    }
}

console.log(copyOcc);

This will output:

{
  18 Dec: 0,
  19 Dec: 1,
  20 Dec: 0,
  21 Dec: 2,
  22 Dec: 0,
  23 Dec: 0,
  24 Dec: 0,
  25 Dec: 0
}

See the following fiddle for the complete script.

Answer 2

I suggest the following solution, written in typescript :

1. Create an array containing the last 7 days, formatted according to the dates in users -array.
2. Iterate through the last 7 dates (using the map -operator) and apply filter for each day to find out how many users joined on the given day.
3. getDailyRegistrations() will return the result you are looking for.

months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
          'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
users = ['19 Dec', '21 Dec', '21 Dec'];


getDailyRegistrations(numberOfDays: number = 7): string[] {
    return this.getLastXDates(numberOfDays)
        .map(d => this.formatDate(d))
        .map(d => `${d}: ${this.users.filter(u => u === d).length}`);
}


/* Helper methods */

private getLastXDates(numbOfDays: number): Date[] {
    return Array.from(Array(numbOfDays).keys()).reverse().map(i => {
        const d = new Date();
        d.setDate(d.getDate() - i);
        return d;
    });
}

private formatDate(d: Date): string {
    const day = d.getDate();
    const month = this.months[d.getMonth()];
    return `${day} ${month}`;
}

Answer 3

Same as above answer but in pure javascript.

const users = ['19 Dec', '21 Dec', '21 Dec']
const month_to_abv = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

// fetch previouse days, default it fetches 7 days
function getPreviouseDaysObj(noOfDays = 7) {
  const obj = {};
  for (let i = 0; i < noOfDays; i++) {
    const curr_date = new Date();
    curr_date.setDate(curr_date.getDate() - i);
    obj[formatDate(curr_date)] = 0;
  }
  return obj;
}
// format date
function formatDate(date) {
  return `${date.getDate()} ${month_to_abv[date.getMonth()]}`
}

// create obj for previouse 7 days
const previouse_days = getPreviouseDaysObj(7);

// calculate occurance
const occurences = users.reduce(function (acc, curr) {
  acc[curr] ? ++acc[curr] : (acc[curr] = 1);
  return acc;
}, Object.assign({}, previouse_days));


// Log to console
console.log(occurences)