输入文字的字数限制

我想在我的文本框中只允许数字，并且对它也有字符限制.

I want to my textbox to only allow numbers and also have a character limit on it.

目前，我正在使用数字...现在我在解决如何限制字符方面遇到问题.

Currently, I have the numbers working... Now I am having issues figuring out how to limit the characters.

这就是我所拥有的...

Here is what I have...

JS:

app.directive('numbersonly', function () {
    return {
        restrict: 'A',
        link: function (scope, elm, attrs, ctrl) {
            elm.on('keydown', function (event) {
                if (event.which == 64 || event.which == 16 && elm.val().length > 4) {
                    return false;
                } else if (event.which >= 48 && event.which <= 57) {
                    return true;
                } else if (event.which >= 96 && event.which <= 105) {
                    return true;
                } else if ([8, 13, 27, 37, 38, 39, 40].indexOf(event.which) > -1 && elm.val().length > 4) {
                    return true;
                } else {
                    event.preventDefault();
                    return false;
                }
            });
        }
    }
});

标记:

<input type="text" id="txtEmpAge" data-ng-model="newemployee.Age" class="form-control" numbersonly required />