How to validate input using javascript

Question

<script type="text/javascript">
function validate() {
    if (document.form.price.value.trim() === "") {
        alert("Please enter a price");
        document.form.price.focus();
        return false;
    }
    if (document.form.price.value !== "") {
        if (! (/^\d*(?:\.\d{0,2})?$/.test(document.form.price.value))) {
            alert("Please enter a valid price");
            document.form.price.focus();
            return false;
        }
    }
    return true;
}
</script>

<form action="" method="post" name="form" id="form" onsubmit="return validate(this);">

<input name="price"  type="text" class="r2" />
<input name="price2" type="text" class="r2" />
<input name="price3" type="text" class="r2" />
<input name="price4" type="text" class="r2" />
<input name="price5" type="text" class="r2" />
...more....
<input name="price50" type="text" class="r2" />

This javascript code is working fine to validate the field "price".

Question :

How to make the code to work as global validation? Example: would validate the price, price2, price3, price4, price5 etc.. with a single function. Please let me know :)

Answer 1

My personal recommendation would be something like this:

<script type="text/javascript">
function validate() {
    return [
        document.form.price,
        document.form.price2,
        document.form.price3,
        document.form.price4,
        document.form.price5
    ].every(validatePrice)
}

function validatePrice(price)
{
    if (price.value.trim() === "") {
        alert("Please enter a price");
        price.focus();
        return false;
    }
    if (price.value !== "") {
        if (! (/^\d*(?:\.\d{0,2})?$/.test(price.value))) {
            alert("Please enter a valid price");
            price.focus();
            return false;
        }
    }
    return true;       
}
</script>

Answer 2

If you do not plan on using jQuery this should work.

function validate() {
    for (var field in document.getElementsByTagName('input')) {
        if (isPriceField(field)) {
            field.value = field.value.trim();
            if (isNaN(parseFloat(field.value))) {
                return alertAndFocus(field, "Please enter a valid price");
            }
        }               
    }

    return true;
}

function isPriceField(field) {
    return (field.name.substr(0, Math.min(5, field.name.length)) === 'price')
}

function alertAndFocus(field, message) {
    alert(message);
    field.focus();
    return false;
}