JSFiddle - React, Tailwind, and code Playground

HTML

<div data-bind="attr: { 'data-member': autofocus().toString() }" style="border:1px solid black">Test</div>
<p><em>(inspect the div element above, then click on the buttons below)</em></p>

<br /><br />
<button data-bind="click: toggleFocus">Toggle focus with strict true/false</button>

<br /><br />
<button data-bind="click: setFocusWithStringTrue">Set focus with string 'true'</button>

<br /><br />
<button data-bind="click: setFocusWithStringFalse">Set focus with string 'false'</button>

JavaScript

var VM = {
    autofocus: ko.observable(false),
    toggleFocus: function() {
        this.autofocus(!this.autofocus());    
    },
    setFocusWithStringTrue: function() {
         this.autofocus('true');   
    },
    setFocusWithStringFalse: function() {
         this.autofocus('false');   
    }
};

ko.applyBindings(VM);