lightning:spinner component

<aura:application controller="echoController" extends="force:slds">
    <lightning:button label="Toggle" variant="brand" onclick="{!c.showSpinner}"/>
    <div class="exampleHolder">
        <lightning:spinner aura:id="mySpinner" class="slds-hide"/>
    </div>
</aura:application>

({
    showSpinner: function (component, event, helper) {
        helper.showSpinner(component);
        var action = component.get('c.echo');
        action.setCallback(this,function(response){
            var state = response.getState();
            if (state === "SUCCESS") {
                helper.hideSpinner(component);
            }
        });
        $A.enqueueAction(action);
    }
})

({
    showSpinner: function (component, event, helper) {
        var spinner = component.find("mySpinner");
        $A.util.removeClass(spinner, "slds-hide");
    },
    
    hideSpinner: function (component, event, helper) {
        var spinner = component.find("mySpinner");
        $A.util.addClass(spinner, "slds-hide");
    }
})

public class echoController {
    @AuraEnabled
    public static String echo(String message) {
     return message;
    }
}