Edit in JSFiddle

var clickToEditViewModel = function(text) {
    var self = this;

    self.editingText = ko.observable(false);
    self.text = ko.observable(text);            
    self.textClick = function() {
        // Set editingText to true.  This will cause the div to
        // hide, the input box to show, and the input box to 
        // receive focus, all of which are bound to editingText.
        // Once the input box loses focus, editingText will be
        // set to false (due to binding), which will cause the
        // input box to hide and the div to show.        

var cteVM = new clickToEditViewModel("Hello World");
<!DOCTYPE html>
<div class="well">

    <h4>Click the text below to edit it.  When done editing, click somewhere else.</h4>
<span class="span1"> </span>    
    <div data-bind="text: text, visible: !editingText(), click: textClick"></div>    
    <input data-bind="value: text, visible: editingText, hasfocus: editingText" type='text'"></input>
    <br />
    <h4>Here is another view of the text property on the viewmodel.  This one is not set up for click-to-edit:</h4>
    <div data-bind="text: text"></div>