如何在按键事件中仅允许特定打印范围内的字符？

Question

<input type="text" name="RangeText" id="rangeNum" onkeypress = "printValidation(event)" />

I am trying to allow only characters on key press event for specific pages range in the above print selection text box. I can do this easily with regex but want user to type only valid sccenarios!

What I want to achive is as shown in below examples:

1 allow

1-2 allow

-2 not allow

1, 2-3, 4, 5-7 allow

1 2, 3 not allow

1-2-2 not allow

This is how my current funtion looks like, the tricky part seems is not allowing negative number to begin with but allow the hyphen in the range!

function printValidation(evt) {
    var charCode = (evt.which) ? evt.which : evt.keyCode;
    if (!evt.shiftKey && !evt.altKey && !evt.ctrlKey && charCode >= 48 && charCode <= 57 || charCode == 188 || charCode == 109) {
        alert("character accepted");
        return true;
    }else {
            alert("illegal character detected");
            return false;
        }
 }

Is there a possibility to achieve this without going in regex way?

Answer 1

I suggest you allow the user to type only valid characters as you are doing (including hyphen, comma and space) and run a regex at the end (when you submit or lose focus of the field). Or you could fill your function with a lot of if to test all the possibilities, ex. allow hyphen only after another character that's not hyphen, comma or space, etc. You can read the content of the field with evt.currentTarget.value . Hope that helps :)