CODEWITHSUNDEEP
javascriptjquery
Jonah
Jonah

Reputation: 283

PayDay Loan APR calculation in Javascript

I'm trying to create a payday loan calculation and I've had help on math.stackexchange.

I've been given a formula to calculate an APR figure.

I have an amount I want to loan £100 I want to pay this back in 14 days. Interest for this loan is 15% The fee for this service is 0.20p per day. From this I calculate the fee to be £17.80.

(100+100×0.15+0.2×14100)365.25/14−1≈70.80

So effectively the APR will be 7080%

How would I calculate this answer in Javasript to two decimal places?

I currently have this but I'm getting the wrong figure.

function update() {            
     $interest = 0.15 ;
     $perday = 20 ;
     $amount1 = $("#amount").val();
     $amount1 = parseInt($amount1, 10) || 100;
     $dayscount = $("#days").val();
     $amount2 = parseInt($amount1) + $interest * parseInt($amount1) + (parseInt($dayscount) * ($perday/100));
     $apr = (($amount2-$amount1 / $amount1 ) / ((parseInt($dayscount)/365.25) * 100));
     $("#amount").text($amount1);
     $("#amount2").text($amount2);
     $("#amount3").text(parseFloat($amount2-$amount1).toFixed(2));
     $("#amount4").text(parseFloat($apr).toFixed(2));     
}

Thanks

Upvotes: 0

Views: 1666

Answers (1)

Evgeny
Evgeny

Reputation: 6290

Change this line

$apr = (($amount2-$amount1 / $amount1 ) / ((parseInt($dayscount)/365.25) * 100));

to this

$apr = Math.pow($amount2 / 100, 365.25 / $dayscount) - 1;

It will give you 70.80

P.S. In Javascript, developers commonly put $ in front of a variable to signal it is a jQuery object. No need to do it here.

Upvotes: 1

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