I wan't to have a conditional css class and a dynamic css class added via the css binding.
Like so:
data-bind="css: {$data.something() : true, open : showOpen() }"
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2 Answers
Clearest is probably to combine them in one computed:
function ViewModel() {
var self = this;
self.something = ko.observable("danger");
self.showOpen = ko.observable(true);
self.cssClass = ko.computed(function() {
return self.something() + (self.showOpen() ? " open" : "");
});
}
ko.applyBindings(new ViewModel());div { padding: 10px; }
.danger { background-color: orange; }
.open { border: 5px solid gray; border-width: 5px 5px 0; }<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/2.2.1/knockout-min.js"></script>
<div data-bind="css: cssClass"> my div with class: <code data-bind="text: cssClass"></code> </div>
<hr>
<label><input type="checkbox" data-bind="checked: showOpen"> showOpen</label>
<br>
<input type="text" data-bind="value: something, valueUpdate: 'afterkeydown'">Allows you to unit test the entire thing, and keeps your view concise.
Comments
I prefer a custom binding like this:
ko.bindingHandlers.klass = {
init: function (el, val) {
var prevClass = null
ko.computed(function () {
if (prevClass)
$(el).removeClass(prevClass);
var newClass = ko.unwrap(val());
$(el).addClass(newClass);
prevClass = newClass;
}, null, {disposeWhenNodeIsRemoved: el})
}
}
var vmo = {
cssClass: ko.observable('a'),
toggle: function () { vmo.cssClass(vmo.cssClass() == 'a' ? 'b' : 'a') }
}
ko.applyBindings(vmo);.a {
color: red;
}
.b {
color: blue;
}
.another {
text-decoration: underline;
}<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<p data-bind='klass: cssClass, css: {another: true}'>Hello</p>
<button data-bind='click: toggle'>Toggle</button>