<aura:attribute name="slider" default="1" type="Integer"/>
.
.
.
<fieldset class="slds-form-element">
<legend class="slds-form-element__legend slds-form-element__label">Slider</legend>
<div class="slds-form-element">
<label class="slds-form-element__label" for="slider-id-01">
<span class="slds-slider-label">
<span class="slds-slider-label__label">Indica il numero di mesi da pianificare:</span>
<span class="slds-slider-label__range">1 - 24</span>
</span>
</label>
<div class="slds-form-element__control">
<div class="slds-slider">
<input aura:id="slider" class="slds-slider__range" type="range" min="1" max="24" step="1" value="{!v.slider}" onchange="{!c.getNumMouthPlanner}" />
<span class="slds-slider__value" aria-hidden="true">{!v.slider}</span>
</div>
</div>
</div>
</fieldset>
Controller
getNumMouthPlanner : function(component,event){
sliderValue = component.find("slider").getElement().value;
console.log(component.find("slider").getElement().value);
component.set("v.slider",sliderValue);
}