Knockout JS valueUpdate keypress not working for enable binding

Question

I have a 'Save' button on my form that has knockout enable binding. I added valueUpdate: 'keypress' to my knockout binding expression hoping for save button to become enabled on keypress. I have a simple input textbox with value knockout binding. Instead, page still requiring user to click away for save button to become enabled. HTML below. when user types in input, canSave becomes true enabling save button.

<button data-bind="click: save, enable: canSave, valueUpdate: 'keypress'">Save</button>

<h3><strong>First Name: <input data-bind="value: firstName"></strong></h3>

Answer 1

The valueUpdate binding only makes sense coupled with a value binding; it should go on your input, not on your button.

<button data-bind="click: save, enable: canSave">Save</button>
<h3><strong>First Name: <input data-bind="value: firstName, valueUpdate: 'keypress'"></strong></h3>

Also, consider valueUpdate: 'input' if you're using browsers new enough to support it, or even the textInput binding, if you're using KO >3.2

Answer 2

Try this:

<button data-bind="click: save, enable: firstName().length > 0">Save</button>

<h3><strong>First Name: <input data-bind="value: firstName, valueUpdate:'keypress'"></strong></h3>

from you're code it seems, firstName is an observable, if so then above code will do what you need. It will disable the button if there is not input else make it enable.