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KnockoutJS - Disable Binding
This binding is the negation of enable binding. This binding disables the associated DOM element when the parameter evaluates to true.
Syntax
disable: <binding-value>
Parameters
Parameter consists of Boolean like value, which decides whether the element should be disabled or not. If the parameter is true or true-like value, then the element is disabled.
Non-Boolean values are considered as loosely Boolean values. Meaning 0 and null are considered as false-like value and Integer and non-null objects are considered as true-like value.
If the condition in parameter contains an observable value, then the condition is re-evaluated whenever the observable value changes. Correspondingly, related markup will be disabled based on the condition result.
Example
Let us take a look at the following example which demonstrates the use of disable binding.
<!DOCTYPE html> <head> <title>KnockoutJS Disable Binding</title> <script src = "https://ajax.aspnetcdn.com/ajax/knockout/knockout-3.3.0.js" type = "text/javascript"></script> </head> <body> <p> Enter your feedback here:<br><br> <textarea rows = 5 data-bind = "value: hasFeedback, valueUpdate: 'afterkeydown'" ></textarea> </p> <p><button data-bind = "disable: !(hasFeedback())">Save Feedback</button></p> <script type = "text/javascript"> function ViewModel () { hasFeedback = ko.observable(''); }; var vm = new ViewModel(); ko.applyBindings(vm); </script> </body> </html>
Output
Let's carry out the following steps to see how the above code works −
Save the above code in disable-bind.htm file.
Open this HTML file in a browser.
The save button is disabled when the user has not entered any feedback.
You can also use a random expression to decide whether element should be disabled or not.
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