calculator.js

const p = 250000 - (20 / 100) * 250000;
    console.log('calcMonthlyRepayment -> p', p);

    // monthly intrest
    let i = (5 / 100 / 12).toFixed(6);
    console.log('calcMonthlyRepayment -> i', i);

    // number of periods (months)
    let n = 30 * 12;
    console.log('calcMonthlyRepayment -> n', n);
    var ab = 1 + 0.004167;
    let m = (p * (i * ab ** n)) / (4.468278 - 1);
    console.log('calcMonthlyRepayment -> m', m);