Using javascript, how can you fill in the missing dates within an array of objects?

I need to populate this object with dates starting from today up to the next 7 days. Here is my current object:

let obj = {
  "sessions": [{
       "id": 0,
       "available_capacity": 3,
       "date": "15-05-2021"
   },
   {
       "id": 1,
       "available_capacity": 5,
       "date": "16-05-2021"
   },
   {
       "id": 2,
       "available_capacity": 2,
       "date": "18-05-2021"
   }]
}

Desired output:

let output = {
  "sessions": [{
       "date": "14-05-2021"
   },
   {
       "id": 0,
       "available_capacity": 3,
       "date": "15-05-2021"
   },
   {
       "id": 1,
       "available_capacity": 5,
       "date": "16-05-2021"
   },
   {
       "date": "17-05-2021"
   },
   {
       "id": 2,
       "available_capacity": 2,
       "date": "18-05-2021"
   },
   {
       "date": "19-05-2021"
   },
   {
       "date": "20-05-2021"
   }]
}

Below is a function that generates an array of dates for the coming week:

function getWeekDates() {
    let dates = [];
    for (let i = 0; i <= 6; i++) {
      dates.push(new Date(Date.now() + 1000 * 3600 * (i * 24)).toLocaleDateString('en-GB').replace('/', '-').replace('/', '-'));
    }
    console.log(dates);
}

getWeekDates();

//result: ["14-05-2021", "15-05-2021", "16-05-2021", "17-05-2021", "18-05-2021", "19-05-2021", "20-05-2021"]

How can I add the missing dates to my object?

javascriptarraysjsondateobject

Answer №1

If you need to create an array of dates, you can utilize the following code snippet. Provide a startDate and the number of days you want in the array. For example, simply use dateRange(new Date(), 7)

const DAY_IN_MS = 24 * 60 * 60 * 1000
const dateRange = (startDate, numOfDays) => {
    const startDateInMs = startDate.getTime()
    return [...Array(numOfDays).keys()].map(i => new Date(startDateInMs + i * DAY_IN_MS).toISOString().slice(0,10))
}

let dates = dateRange(new Date(),7);
console.log(dates);

To check if a certain date exists in obj.sessions, you can make use of Array.prototype.map and utilize Array.prototype.find. If the date is found, return the object; otherwise, return the same date. Array.prototype.find will return undefined if the item is not found.

let obj = {
  "sessions": [{
       "id": 0,
       "available_capacity": 3,
       "date": "15-05-2021"
   },
   {
       "id": 1,
       "available_capacity": 5,
       "date": "16-05-2021"
   },
   {
       "id": 2,
       "available_capacity": 2,
       "date": "18-05-2021"
   }]
}
function getWeekDates() {
    let dates = [];
    for (let i = 0; i <= 6; i++) {
      dates.push(new Date(Date.now() + 1000 * 3600 * (i * 24)).toLocaleDateString('en-GB').replace('/', '-').replace('/', '-'));
    }
    return dates;
}

let dates = getWeekDates();
let r = dates.map(d => {
  let o = obj.sessions.find(x => x.date === d);
  return o ?? {date: d}
 });
console.log(r);

Answer №2

If you're searching for something similar to the following:


function retrieveWeekDates() {
    let dates = [];
    for (let i = 0; i <= 6; i++) {
      dates.push(new Date(Date.now() + 1000 * 3600 * (i * 24)).toLocaleDateString('en-GB').replace('/', '-').replace('/', '-'));
    }
    return dates
}
retrieveWeekDates().map(date => {
    return obj.sessions.find(s => s.date === date) || date
})


/* 

Results

[
    {
        "date": "14-05-2021"
    },
    {
        "id": 0,
        "available_capacity": 3,
        "date": "15-05-2021"
    },
    {
        "id": 1,
        "available_capacity": 5,
        "date": "16-05-2021"
    },
    {
        "date": "17-05-2021"
    },
    {
        "id": 2,
        "available_capacity": 2,
        "date": "18-05-2021"
    },
    {
        "date": "19-05-2021"
    },
    {
        "date": "20-05-2021"
    }
]
*/

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