6

I have developed a code in which adds values and at the end subtracts the smallest value based on the items you select in a form. The code works fine however the problem occurs when you unselect all the items and instead of displaying 0, it displays -Infinity. What do I do to this script to force it to display 0 instead of -Infinity?

// All selected prices are stored on a array
var prices = [];

// A function to remove a item from an array
function remove(array, item) {
    for (var i = 0, len = array.length; i < len; i++) {
        if (array[i] == item) {
            array.splice(i, 1);
            return true;
        }
    }
    return false;
}

function calculateSectedDues(checkbox, amount) {
    // We add or remove the price as necesary

    if (checkbox.checked) {
        prices.push(amount);
    } else {
        remove(prices, amount);
    }

    // We sum all the prices
    var total = 0;
    for (var i = 0, len = prices.length; i < len; i++)
        total += prices[i];

    // We get the lower one
    var min = Math.min.apply(Math, prices);

    // And substract it
    total -= min;

    // Please, don't access the DOM elements this way, use document.getElementById instead
    document.grad_enroll_form.total.value = total;

}


</script>
Jeremy
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1 Answers1

6

Math.min() with no arguments returns Infinity, which is what happens when you call Math.min.apply(Math, prices) with an empty prices array.

Why not just detect the presence of an Infinity minimum and reset it to zero?

// We get the lower one
var min = Math.min.apply(Math, prices);

// ** test for Infinity **
if(min == Infinity) { min = 0; }

// And substract it
total -= min;

Or make sure prices has at least one element:

// fill the empty array with a zero
if(prices.length == 0) prices.push(0);

// We get the lower one
var min = Math.min.apply(Math, prices);
apsillers
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  • @Alfie_Fitz Trailing zeros are dropped in JavaScript. You can use `.toFixed(2)` to show the number as a string with two decimal places. (Take a look at [Is JavaScript's Floating-Point Math Broken?](http://stackoverflow.com/questions/588004/is-javascripts-floating-point-math-broken) to understand general problems with floating point numbers.) – apsillers Apr 16 '13 at 21:01