Disable button when all select options selected (Lightning)

DemoBundle.cmp

<aura:application >
    <aura:attribute name="opts" type="String[]" default="['A','B','C']" />
    <aura:attribute name="disableButton" type="Boolean" default="false" />
    <select aura:id="picklist" onchange="{!c.updateButtonState}" multiple="multiple">
    	<aura:iteration items="{!v.opts}" var="opt">
        	<option value="{!opt}">{!opt}</option>
        </aura:iteration>
    </select>
    <lightning:button label="Test Button" disabled="{!v.disableButton}" />
</aura:application>

DemoBundleController.js

({
    updateButtonState: function(component, event, helper) {
        // Get the select options
        let items = component.find("picklist").getElement().options;
        // Set to disabled when all options selected
        component.set("v.disableButton", Array.prototype.every.call(items, option => option.selected));
        // NOTE: This code also re-enables button when one item is deselected.
        // If not desirable, you will need to slightly modify this code.
    }
})