This seems to be a simple issue but I can't seem to figure it out

I just need to display the length of a string that is observable. I have tried achieving the result with a koputed() function as you can see in the code below, but it always returns zero.

Fiddle with an example

Html

<div id="vm"> 
    <h2>The title is: <span data-bind="text: title"></span></h2>
    <h2>The length is: <span data-bind="text: title.length"></span></h2>
    <h2>Length from puted: <span data-bind="text: titleLength"></span></h2>
    <input data-bind="value: title, valueUpdate: 'keyup'"/>
</div>

JavaScript

function VM() {
    var self = this;
    self.title = ko.observable();
    self.titleLength = koputed(function() {
        return self.title.length;
    });
}

ko.applyBindings(VM(), document.getElementById('vm'));

This seems to be a simple issue but I can't seem to figure it out

I just need to display the length of a string that is observable. I have tried achieving the result with a ko.puted() function as you can see in the code below, but it always returns zero.

Fiddle with an example

Html

<div id="vm"> 
    <h2>The title is: <span data-bind="text: title"></span></h2>
    <h2>The length is: <span data-bind="text: title.length"></span></h2>
    <h2>Length from puted: <span data-bind="text: titleLength"></span></h2>
    <input data-bind="value: title, valueUpdate: 'keyup'"/>
</div>

JavaScript

function VM() {
    var self = this;
    self.title = ko.observable();
    self.titleLength = ko.puted(function() {
        return self.title.length;
    });
}

ko.applyBindings(VM(), document.getElementById('vm'));

• javascript
• knockout.js

1 Answer 1

Your puted version is almost correct. Change it by this

return self.title().length; // <-- Notice () after title

DEMO