Javascript Help - prevent duplicate characters in textbox

问题

Looking for a bit of help to modify some already-working JavaScript.

I am using a piece of JavaScript along with a filtered textbox, the filtered text box only allows {1234567890,-}

The below JavaScript works and prevents the user from entering more than 1 decimal I want to also add a dash/minus {-} to the allowed characters and prevent duplicates

    <script type="text/javascript">

    function PreventDuplicateDecimal(evt) {
        var charCode = (evt.which) ? evt.which : event.keyCode;
        var itemdecimal = evt.srcElement.value.split('.');
        if (itemdecimal.length > 1 && charCode == 46)
            return false;
        return true;
    }
</script>

I have tried adding;

I have tried adding var itemdash = evt.srcElement.value.split('-'); and adding it as a 'or' statement but no luck

Any help would be much appreciated

Thanks in advance Paul

回答1:

if(evt.srcElement.value.indexOf(".") > -1) {
    if (charCode === 46) {
        return false;
    }
}
if(evt.srcElement.value.indexOf("-") > -1) {
    if (charCode === 45) {
        return false;
    }
}
return true;

来源：https://stackoverflow.com/questions/22000283/javascript-help-prevent-duplicate-characters-in-textbox