CODEWITHSUNDEEP
javascripthtmlmath
AL_1
AL_1

Reputation: 112

Doing an equation in javascript?

I have this code and it always outputs 9 no mater what number i put in the textbbox. The equation is 0.25x^(2)+9, the ^(2) means squared.

<html>
<head>
    <script>
    function calc() {
        var number = parseInt(document.getElementById('input').value);
        var one = parseInt(0.25*number);
        var two = parseInt(one*one);
        var three = parseInt(two+9) ;
        var sum = parseInt(three);
        document.getElementById('num').innerHTML = sum;
    }
    </script>
</head>
<body>
<p>$10 fee and 2 Commands are free!</p>
<input id="input" type="number" name="quantity" min="1" max="1000"></input><div id="num"></div>
<button onclick="calc()">Calculate</button>
</body>

help?

Fiddle

Upvotes: 1

Views: 112

Answers (2)

Donat Pants
Donat Pants

Reputation: 369

I think that when you are casting it to an int everytime you are rounding everything down to 0 and then when you add +9 you alwasy get 9 as the answer so do:

    function calc() {
        var number = parseInt(document.getElementById('input').value);
        var one = 0.25*number;
        var two = one*one;
        var three = two+9;
        var sum = three;
        document.getElementById('num').innerHTML = sum;
    }

In addtion you have a methmetical mistake

var one = 0.25*number;
var two = one*one;

two will be like saying two = o.25^2 * x^2 and not two = 0.25 * x^2 like you want so change it to:

function calc() {
        var number = parseInt(document.getElementById('input').value);
        var one = number*number;
        var two = 0.25*one;
        var three = two+9;
        var sum = three;
        document.getElementById('num').innerHTML = sum;
    }

And there is an even easyer way:

        function calc() {
            var number = parseInt(document.getElementById('input').value);
            var sum = 0.25*(number*number) + 9;
            document.getElementById('num').innerHTML = sum;
        }

Upvotes: 0

gurvinder372
gurvinder372

Reputation: 68393

I have this code and it always outputs 9 no mater what number i put in the textbbox

That is because when you do (0.25 * 0.25), it becomes 0.625. and parseInt on it makes it 0.

Which means unless your number is less than 4, it will always print 9 since (0+9) -> 9 (0 after parseInt)

Also, your code is outputting 10 if number is 4 and 13 if number is 8.

Right formula would be

sum = Math.pow( number * 0.25, 2 ) + 9

Upvotes: 4

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