javascript - knockout variable not defined -

I'm relatively new to Knockout.js and I'm having trouble doing this calculable job. In short, I would like to disable a button until the tapetera is input. For Textarea:

  & lt; Textarea class = "form-control" id = "note" name = "note" data-bind = "value: text1, value update: 'keyboard' placeholder =" note ... "& gt; & lt ; / Textarea> For  

button:

    Note Save & lt; / btn & gt;  

And here is my .js:

  var vm = {text1: k.a. ("") ,} Vm.hasInput = ko.computed (function () {return.text1 ();}, vm); ko.applyBindings (VM);  

Run in firebugs Yes, I get an error from the console which reads:

Reference: Error: Lesson 1 is not defined

I should add that I can add my code To make this reference, I am referring to:

Edit: "click: addNote" part of the button was for something else I forgot to delete it in this snippet because "addNote" functionality Just working fine. I am sorry for the illusion and I thank you for seeing it all. Because of this, it seems that T.J. My question has been answered, I was working improperly within the binding view modal and the struggle was being fought due to binding.

I think you see an old error message with your VM as shown in your question The problem is that you do not have addNote defined anywhere, but you are trying to force it to click on .

If you add it and make your BTN element an actual button , then all is well:

< Div class = "snippet" data-lang = "JS" data-hide = "wrong">

  var vm = {text1: to .observable (""),}; Vm.hasInput = ko.computed (function () {return.text1 ();}, vm); Vm.addNote = function () {}; // & lt; === Added ko.applyBindings (vm);  

  & lt; Textarea class = "form-control" id = "note" name = "note" data-bound = "value: text1, value update: 'keep'" placeholder = "Enter note ..." & gt; & Lt; / Textarea & gt; & Lt; Button type = "button" class = "btn-btn-kill" id = "saveNote" href = "javascript: zero (0);" Data-bind = "click: addNote, enable: hasInput" & gt; & Lt; I class = "icon-save" & gt; & Lt; / I & gt; Save note & lt; / Button & gt; & Lt; Script src = "https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"> gt; Side note: Just completely FWIW, I have new syntax for  ko.computed