Utilizing a standard variable to apply a CSS property in Knockout JS

Is it possible to set a css property using an if condition with a regular variable instead of observables? Here's an example:

a.html file:

<span class="label" data-bind="text: isApproved, css: sampleglobalvar == true ? 'label-success' : 'label-important'"></span>

a.js file:

Edit:

define('durandal/app'],function(app) {
   var a = function() {

    sampleglobalvar = 'true'
    };
}

However, I am encountering an error stating that 'sampleglobalvar' does not exist in the viewmodel. While I understand that observables should be used, I faced issues when switching between 'true' and 'false' values for observables:

For instance, using:

sampleglobalvar = ko.observable("");

and setting it like this:

if(//condition)
{

sampleglobalvar(true);
}
else
{
sampleglobalvar(false);
}

did not clear the observable properly, leading to unexpected results.

In conclusion, is there a way to utilize a regular JavaScript variable in the css data-bind property?

Answer №1

Achieving true global functionality is indeed possible. However, in order to access global variables (e.g., those stored on the window object), you will need to properly scope the variable within your databinding.

For example:

function RootViewModel() {  
  // Plain property on the "global" (i.e. Root) view model:
  this.plainProp = true;
  
  // True "global" variable:
  window.myGlobal = true;
}

ko.applyBindings(new RootViewModel());
.error { background: red; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.0/knockout-min.js"></script>

<p data-bind="css: plainProp === true ? 'error' : 'plain'">Root plain prop</p>
<p data-bind="css: window.myGlobal === true ? 'error' : 'plain'">Global plain prop</p>

Your question involves function scopes and a potential module loader (such as requirejs?), but with proper scoping for that specific scenario, it should operate similarly to the provided example. If you encounter an issue with a particular aspect, I recommend posing a separate inquiry, complete with a Minimal Repro (comprising more syntactically valid code than presently available).

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