Need help for Javascript
<p>I need a little help in javascript. I am using a simple js file for a little online store. The url of the demo page is: <a href="http://www.k-prim.biz/Esther/Store/proba.html" rel="nofollow">http://www.k-prim.biz/Esther/Store/proba.html</a>
The javascript that I am using is called orderform04.js. There is a bug: when entering q-ty 3 for product1 - at price 4.8 the result is 14.399999999999999 instead of 14.4!</p>

<p>Can anybody help with this issue?</p>

<p>the javascript is here too:</p>

<pre><code>function OrderForm(prefix, precision, firstChoice) {

this.prefix = prefix ? prefix : '';

// ****************************
// Configure here
// ****************************
// names - Set these according to how the html ids are set
this.FORM_NAME = this.prefix + 'frmOrder';
this.BTN_TOTAL = this.prefix + 'btnTotal';
this.TXT_OUT = this.prefix + 'txtTotal';

// partial names - Set these according to how the html ids are set
this.CHK = this.prefix + 'chk';
this.SEL = this.prefix + 'sel';
this.PRICE = this.prefix + 'txtPrice';

// precision for the decimal places
// If not set, then no decimal adjustment is made
this.precision = precision ? precision : -1;

// if the drop down has the first choice after index 1
// this is used when checking or unchecking a checkbox
this.firstChoice = firstChoice ? firstChoice : 1;
// ****************************

// form
this.frm = document.getElementById(this.FORM_NAME);

// checkboxes
this.chkReg = new RegExp(this.CHK + '([0-9]+)');
this.getCheck = function(chkId) {
    return document.getElementById(this.CHK + chkId);
};

// selects
this.selReg = new RegExp(this.SEL + '([0-9]+)');
this.getSelect = function(selId) {
    return document.getElementById(this.SEL + selId);
};

// price spans
this.priceReg = new RegExp(this.PRICE + '([0-9]+)');

// text output
this.txtOut = document.getElementById(this.TXT_OUT);

// button
this.btnTotal = document.getElementById(this.BTN_TOTAL);

// price array
this.prices = new Array();

var o = this;
this.getCheckEvent = function() {
    return function() {
        o.checkRetotal(o, this);
    };
};

this.getSelectEvent = function() {
    return function() {
        o.totalCost(o);
    };
};

this.getBtnEvent = function() {
    return function() {
        o.totalCost(o);
    };
};

/*
 * Calculate the cost
 * 
 * Required:
 *  Span tags around the prices with IDs formatted
 *  so each item's numbers correspond its select elements and input checkboxes.
 */
this.totalCost = function(orderObj) {
    var spanObj = orderObj.frm.getElementsByTagName('span');
    var total = 0.0;
    for (var i=0; i&lt;spanObj.length; i++) {
        var regResult = orderObj.priceReg.exec(spanObj[i].id);
        if (regResult) {
            var itemNum = regResult[1];
            var chkObj = orderObj.getCheck(itemNum);
            var selObj = orderObj.getSelect(itemNum);
            var price = orderObj.prices[itemNum];
            var quantity = 0;
            if (selObj) {
                quantity = parseFloat(selObj.options[selObj.selectedIndex].text);
                quantity = isNaN(quantity) ? 0 : quantity;
                if (chkObj) chkObj.checked = quantity;
            } else if (chkObj) {
                quantity = chkObj.checked ? 1 : 0;
            }
            total += quantity * price;
        }
    }
    if (this.precision == -1) {
        orderObj.txtOut.value = total
    } else {
        orderObj.txtOut.value = total.toFixed(this.precision);
    }
};

/*
 * Handle clicks on the checkboxes
 *
 * Required:
 *  The corresponding select elements and input checkboxes need to be numbered the same
 *
 */
this.checkRetotal = function(orderObj, obj) {
    var regResult = orderObj.chkReg.exec(obj.id);
    if (regResult) {
        var optObj = orderObj.getSelect(regResult[1]);
        if (optObj) {
            if (obj.checked) {
                optObj.selectedIndex = orderObj.firstChoice;
            } else {
                optObj.selectedIndex = 0;
            }
        }
        orderObj.totalCost(orderObj);
    }
};

/*
 * Set up events
 */
this.setEvents = function(orderObj) {
    var spanObj = orderObj.frm.getElementsByTagName('span');
    for (var i=0; i&lt;spanObj.length; i++) {
        var regResult = orderObj.priceReg.exec(spanObj[i].id);
        if (regResult) {
            var itemNum = regResult[1];
            var chkObj = orderObj.getCheck(itemNum);
            var selObj = orderObj.getSelect(itemNum);
            if (chkObj) {
                chkObj.onclick = orderObj.getCheckEvent();
            }
            if (selObj) {
                selObj.onchange = orderObj.getSelectEvent();
            }
            if (orderObj.btnTotal) {
                orderObj.btnTotal.onclick = orderObj.getBtnEvent();
            }
        }
    }
};
this.setEvents(this);

/*
 *
 * Grab the prices from the html
 * Required:
 *  Prices should be wrapped in span tags, numbers only.
 */
this.grabPrices = function(orderObj) {
    var spanObj = orderObj.frm.getElementsByTagName('span');
    for (var i=0; i&lt;spanObj.length; i++) {
        if (orderObj.priceReg.test(spanObj[i].id)) {
            var regResult = orderObj.priceReg.exec(spanObj[i].id);
            if (regResult) {
                orderObj.prices[regResult[1]] = parseFloat(spanObj[i].innerHTML);
            }
        }
    }
};
this.grabPrices(this);
</code></pre>

<p>}</p>
