Get all dates from first date of week in Array of objects in JavaScript

Question

Need help on solving this, should be a small task, but could not figured it out.

Problem: data is an array of objects with the first date of the week in x and a value for that week in y. need a solution/function that will return all dates in that week in x and the same value in y for each date in that particular week. I'm using moment.js in case needed.

Input:

data = 
    [
        {
            "x": "2022-07-25",
            "y": 0.5
        },
        {
            "x": "2022-08-01",
            "y": 0.2
        },
        {
            "x": "2022-08-08",
            "y": 0.3
        }
    ]

Expected output:

data = 
    [
        {
            "x": "2022-07-25",
            "y": 0.5
        },
    {
            "x": "2022-07-26",
            "y": 0.5
        },
    {
            "x": "2022-07-27",
            "y": 0.5
        },
    {
            "x": "2022-07-28",
            "y": 0.5
        },
    {
            "x": "2022-07-29",
            "y": 0.5
        },
    {
            "x": "2022-07-30",
            "y": 0.5
        },
    {
            "x": "2022-07-31",
            "y": 0.5
        },
        {
            "x": "2022-08-01",
            "y": 0.2
        },
    {
            "x": "2022-08-02",
            "y": 0.2
        },
    {
            "x": "2022-08-03",
            "y": 0.2
        },
    {
            "x": "2022-08-04",
            "y": 0.2
        },
    {
            "x": "2022-08-05",
            "y": 0.2
        },
    {
            "x": "2022-08-06",
            "y": 0.2
        },
    {
            "x": "2022-08-07",
            "y": 0.2
        },
        {
            "x": "2022-08-08",
            "y": 0.3
        },{
            "x": "2022-08-09",
            "y": 0.3
        }
    ,{
            "x": "2022-08-10",
            "y": 0.3
        }
    ,{
            "x": "2022-08-11",
            "y": 0.3
        },{
            "x": "2022-08-12",
            "y": 0.3
        },{
            "x": "2022-08-13",
            "y": 0.3
        },{
            "x": "2022-08-14",
            "y": 0.3
        }
    ]

score 1 · Answer 1 · answered Sep 05 '22 at 14:33

You could do this by using flatMap and an extension for addDays found in this answer

const data = [{
    "x": "2022-07-25",
    "y": 0.5
  },
  {
    "x": "2022-08-01",
    "y": 0.2
  },
  {
    "x": "2022-08-08",
    "y": 0.3
  }
]

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

const result = data.flatMap(item => {
  
  const date = new Date(item.x)
  
  return [0,1,2,3,4,5,6,7].map(d => (
    {
       x: date.addDays(d).toISOString(), 
       y: item.y
    }       
  ));
})

console.log(result)

In this case only need to get the date, so `.toISOString().split('T').at(0)` — A1exandr Belan, Sep 05 '22 at 14:45

Nick Vu · Accepted Answer · 2022-09-05T14:24:34.880

You can try with reduce

const data = [{
    "x": "2022-07-25",
    "y": 0.5
  },
  {
    "x": "2022-08-01",
    "y": 0.2
  },
  {
    "x": "2022-08-08",
    "y": 0.3
  }
]


const finalResult = data.reduce((result, current) => {
  const {
    x,
    y
  } = current
 
  //convert the string date to a date type
  const currentDate = new Date(x)
  
  //add the current date to the result by default
  result.push(current)

  const days = 6

  for (let day = 1; day <= days; day++) {
    //change the current date to the next date
    currentDate.setDate(currentDate.getDate() + 1)
    //add the new date data to the result
    result.push({
      x: currentDate.toISOString().substring(0, 10),
      y: y
    })
  }

  return result
}, [])

console.log(finalResult)

score 0 · Answer 3 · answered Sep 05 '22 at 14:32

Try this!

const expandEveryWeek = function(data){
    //Array for result
    const result = [];

    //Iterate all array parameters (Assuming first element is the first of week)
    //It's always Monday
    for(const obj of data){
        const {x,y} = obj; //Extract values (x,y)
        const date = new Date(x); //Create date with x
        for(let j=0;j<7;j++){
            result.push({ x : date.toISOString().substring(0,10), y}); //Insert first (0 index)
            date.setDate(date.getDate() + 1) //Add day
        }
    }
    return result;
}

Ok so, pass data object to above function.

The assumption is that each element of this array contains a date that always indicates the Monday of the week to expand

Iterate all obj inside data and for every one extract <date,value>. For every date, iterate other 7 step (one for the start date and other 6 for following days and increment date of one single day, after this, push it inside array with his value y.

Get all dates from first date of week in Array of objects in JavaScript

3 Answers3