Using while- loops instead of for-loops in Javascript

Question

In my script I used a for-loop to calculate the interest over an amount of money. I set the loop to 20 times. Now I'm trying to use a while-loop instead, to calculate the amount of money until the balance is doubled.

var btn = document.getElementById('btn');
var startBalance = document.getElementById('input1');
var percentage = document.getElementById('input2');
var output = document.getElementById('result');

btn.onclick = showBalance;

function showBalance() {
    var factor = 1 + percentage.value / 100;
    var newBalance = +startBalance.value * factor;
    var result = "";

    for (var i = 0; i <= 10; i++) {
        result += "Year " + i + ": €";
        result += newBalance.toFixed(2) + "<br>";
        newBalance *= factor;
    }

    output.innerHTML = result;
}

How do I use a while-loop in this case? Thank you.

Rijad Husic · Accepted Answer · 2020-04-30 08:44:31Z

2

Try this

var btn = document.getElementById('btn');
var startBalance = document.getElementById('input1');
var percentage = document.getElementById('input2');
var output = document.getElementById('result');

btn.onclick = showBalance;

function showBalance() {
        var factor = 1 + percentage.value / 100;
        var startingBalance = startBalance.value;
        var newBalance =+ startingBalance * factor;
        var result = "";
        var i = 0;

   while (newBalance <= startingBalance*2) {
        result += "Year " + i + ": €";
        result += newBalance.toFixed(2) + "<br>";
        newBalance *= factor;
        i++;
    }

    output.innerHTML = result;
}

answered Apr 30, 2020 at 8:44

Rijad Husic

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Comments

Nina Scholz · Accepted Answer · 2020-04-30 08:42:37Z

0

You could calculate the needed years with equation factor^years = 2 and get the final value with a while loop.

var amount = 100,
    factor = 1.02,
    i = 0,
    years = Math.ceil(Math.log(2) / Math.log(factor));

while (i++ < years) amount *= factor;

console.log('years', Math.log(2) / Math.log(factor));
console.log('total', amount);

answered Apr 30, 2020 at 8:42

Nina Scholz

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