/*
Strip whitespace from the beginning and end of a string
Input : a string
*/
function trim(str)
{
    return str.replace(/^\s+|\s+$/g,'');
}

/*
Make sure that textBox only contain number
*/
function checkNumber(textBox)
{
    while (textBox.value.length > 0 && isNaN(textBox.value)) {
        textBox.value = textBox.value.substring(0, textBox.value.length - 1)
    }
    
    textBox.value = trim(textBox.value);
/*  if (textBox.value.length == 0) {
        textBox.value = 0;      
    } else {
        textBox.value = parseInt(textBox.value);
    }*/
}

/*
    Check if a form element is empty.
    If it is display an alert box and focus
    on the element
*/
function isEmpty(formElement, message) {
    formElement.value = trim(formElement.value);
    
    _isEmpty = false;
    if (formElement.value == '') {
        _isEmpty = true;
        alert(message);
        formElement.focus();
    }
    
    return _isEmpty;
}

/*
    Set one value in combo box as the selected value
*/
function setSelect(listElement, listValue)
{
    for (i=0; i < listElement.options.length; i++) {
        if (listElement.options[i].value == listValue)  {
            listElement.selectedIndex = i;
        }
    }   
}