How can I use Javascript to calculate the daily price increase over a specific timeframe?

Question

How can I use Javascript to calculate the daily price increase over a specific timeframe?

I have searched extensively, but I couldn't find anyone discussing this particular topic.

Between April 1st and August 1st, a price starting at $900 gradually increases to $1500. This amounts to approximately $5 per day, with the following formula:

ROUND(1500 - (600 * ((DEADLINE - TODAY) / (DEADLINE - START)))

My challenge is converting this formula into JavaScript and HTML so that I can display it in a sentence like "Today you'll have to pay $920."

This is my progress so far, but I am struggling to reset today's date for accurate calculations:

<div id="foo"></div>


  <script type="text/javascript">

      function getDayDiff(a, b) {
        return (a - b) / 8.64e7;
    }

    function getPayAmount(DEADLINE, TODAY, START) {
        return Math.round(1500 - (600 * getDayDiff(DEADLINE, TODAY) / getDayDiff(DEADLINE, START)));
    }
    
 document.getElementById("foo").innerHTML = "Today you'll have to pay $"  + getPayAmount(new Date(2021, 08, 1), new Date(), new Date(2021, 4, 1));
    </script>

javascript arrays function date math

Answer 1

Answer №1

Begin by determining the number of days since Unix time, utilizing the getTime() method to obtain milliseconds, then apply the same calculation.

const days = (date) => Math.ceil(date.getTime() / (24 * 60 * 60 * 1000));

const DEADLINE = days(new Date("2021-08-01"));
const START = days(new Date("2021-04-01"));
const TODAY = days(new Date());

const res = Math.round(1500 - 600 * ((DEADLINE - TODAY) / (DEADLINE - START)));

console.log(res);

document.querySelector('.adbox.adred').append(`Today's Rate ${res}`)

Answer 2

Begin by determining the number of days since Unix time, utilizing the getTime() method to obtain milliseconds, then apply the same calculation.

const days = (date) => Math.ceil(date.getTime() / (24 * 60 * 60 * 1000));

const DEADLINE = days(new Date("2021-08-01"));
const START = days(new Date("2021-04-01"));
const TODAY = days(new Date());

const res = Math.round(1500 - 600 * ((DEADLINE - TODAY) / (DEADLINE - START)));

console.log(res);

document.querySelector('.adbox.adred').append(`Today's Rate ${res}`)

Answer 3

Answer №2

Here’s a way to achieve this using JavaScript:

    function calculateDayDifference(start, end) {
        return (end - start) / 8.64e7;
    }

    function calculatePaymentAmount(deadline, today, start) {
        return Math.round(1500 - (600 * calculateDayDifference(deadline, today) / calculateDayDifference(deadline, start)));
    }
    
    document.getElementById("output").innerHTML = "You need to pay $" + calculatePaymentAmount(new Date(2021, 12, 31), new Date(2021, 4, 3), new Date(2021, 1, 1));

<div id="output"></div>

Explanation:

8.64e7 represents the number of milliseconds in a day
Date differences are calculated in milliseconds
The payment amount is rounded using Math.round

Additional Note

An alternative method shared is as follows:

<div id="output"></div>


  <script type="text/javascript">

      function calculateDayDifference(start, end) {
        return (end - start) / 8.64e7;
    }

    function calculatePaymentAmount(deadline, today, start) {
        return Math.round(1500 - (600 * calculateDayDifference(deadline, today) / calculateDayDifference(deadline, start)));
    }
    
 document.getElementById("output").innerHTML = "Today's payment: $"  + calculatePaymentAmount(new Date(2021, 08, 1), new Date(2021, 4, 6), new Date(2021, 4, 1));
    </script>

To reset the time portion and focus on the date only, you can use:

 var currentDate = new Date();
 currentDate.setHours(0, 0, 0);
 document.getElementById("output").innerHTML = "Amount due today: $"  + calculatePaymentAmount(new Date(2021, 08, 1, 0, 0, 0), currentDate, new Date(2021, 4, 1, 0, 0, 0));

Answer 4

Here’s a way to achieve this using JavaScript:

    function calculateDayDifference(start, end) {
        return (end - start) / 8.64e7;
    }

    function calculatePaymentAmount(deadline, today, start) {
        return Math.round(1500 - (600 * calculateDayDifference(deadline, today) / calculateDayDifference(deadline, start)));
    }
    
    document.getElementById("output").innerHTML = "You need to pay $" + calculatePaymentAmount(new Date(2021, 12, 31), new Date(2021, 4, 3), new Date(2021, 1, 1));

<div id="output"></div>

Explanation:

8.64e7 represents the number of milliseconds in a day
Date differences are calculated in milliseconds
The payment amount is rounded using Math.round

Additional Note

An alternative method shared is as follows:

<div id="output"></div>


  <script type="text/javascript">

      function calculateDayDifference(start, end) {
        return (end - start) / 8.64e7;
    }

    function calculatePaymentAmount(deadline, today, start) {
        return Math.round(1500 - (600 * calculateDayDifference(deadline, today) / calculateDayDifference(deadline, start)));
    }
    
 document.getElementById("output").innerHTML = "Today's payment: $"  + calculatePaymentAmount(new Date(2021, 08, 1), new Date(2021, 4, 6), new Date(2021, 4, 1));
    </script>

To reset the time portion and focus on the date only, you can use:

 var currentDate = new Date();
 currentDate.setHours(0, 0, 0);
 document.getElementById("output").innerHTML = "Amount due today: $"  + calculatePaymentAmount(new Date(2021, 08, 1, 0, 0, 0), currentDate, new Date(2021, 4, 1, 0, 0, 0));

Answer 5

Answer №3

While there is room for optimization, I wanted to demonstrate how you can utilize all the variables effectively.

// Define two dates and assign them to variables
let dateStart = new Date("04/01/2020");
let dateEnd = new Date("08/01/2020");

// Calculate time difference between the two dates
let timeDifference = dateEnd.getTime() - dateStart.getTime();

// Calculate number of days between the dates
let daysDifference = timeDifference / (1000 * 3600 * 24);

// Set initial and final price values
let initialPrice = 900;
let finalPrice = 1500;

// Calculate price difference
let priceDifference = finalPrice - initialPrice;

// Determine price change over time period in two decimal places
let PriceChangeOverPeriod = (priceDifference / daysDifference).toFixed(2);

document.write(PriceChangeOverPeriod);

Experience the code live at: https://jsfiddle.net/ugzn2y7s/

Answer 6

While there is room for optimization, I wanted to demonstrate how you can utilize all the variables effectively.

// Define two dates and assign them to variables
let dateStart = new Date("04/01/2020");
let dateEnd = new Date("08/01/2020");

// Calculate time difference between the two dates
let timeDifference = dateEnd.getTime() - dateStart.getTime();

// Calculate number of days between the dates
let daysDifference = timeDifference / (1000 * 3600 * 24);

// Set initial and final price values
let initialPrice = 900;
let finalPrice = 1500;

// Calculate price difference
let priceDifference = finalPrice - initialPrice;

// Determine price change over time period in two decimal places
let PriceChangeOverPeriod = (priceDifference / daysDifference).toFixed(2);

document.write(PriceChangeOverPeriod);

Experience the code live at: https://jsfiddle.net/ugzn2y7s/

Answer 7

Answer №4

I calculated the payment rate using the starting, end, and current date,

Then I determined the amount that should have been paid today by adding the rate to the starting amount

const today = new Date();
const startDate = new Date('April 1, 2021');
const endDate = new Date('August 1, 2021');
const deadline = (endDate - startDate) / (1000 * 60 * 60 * 24);
const daysDiff = (today - startDate) / (1000 * 60 * 60 * 24);

const rate = Math.round((1500 - 900) / deadline);

document.body.innerText = `The expected payment for today should be $${Math.round((daysDiff * rate) + 900)}`;

Answer 8

I calculated the payment rate using the starting, end, and current date,

Then I determined the amount that should have been paid today by adding the rate to the starting amount

const today = new Date();
const startDate = new Date('April 1, 2021');
const endDate = new Date('August 1, 2021');
const deadline = (endDate - startDate) / (1000 * 60 * 60 * 24);
const daysDiff = (today - startDate) / (1000 * 60 * 60 * 24);

const rate = Math.round((1500 - 900) / deadline);

document.body.innerText = `The expected payment for today should be $${Math.round((daysDiff * rate) + 900)}`;

How can I use Javascript to calculate the daily price increase over a specific timeframe?

Answer №1

Answer №2

Answer №3

Answer №4

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