Max characters in a textbox with knockout

by sderico

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/knockout/2.1.0/knockout-min.js"></script>
<textarea data-bind="value: comment, valueUpdate: 'afterkeydown'"></textarea>

<br/><br/>
<span data-bind="text: count"></span> characters

JavaScript

var viewModel = function(){
    var self = this;
    
    self.comment = ko.observable("");
    self.count = ko.computed(function(){
        self.comment(self.comment().substring(0, 10));
        var countNum = 10 - self.comment().length;
        return countNum
    });
}
    
    
var vm = new viewModel();
ko.applyBindings(vm);