UI -
<aura:component >
    <aura:attribute name="msg" type="String" default="Error"/>
    <aura:attribute name="msgType" type="String" default="success"/>
	<div id="responseErrors" class="{!'slds-notify slds-notify--alert slds-theme--'+v.msgType+' slds-theme--inverse-text slds-theme--alert-texture'}" role="alert">
        <span class="slds-assistive-text">Info</span>
        <lightning:buttonIcon iconName="utility:close" alternativeText="close" class="slds-button slds-button--icon-inverse slds-notify__close" onclick="{!c.close}"/>
        <h2>{!v.msg}</h2>
    </div>
</aura:component>

Controller Js -
({
	close : function(cmp, event, helper) {
		cmp.set("v.msg",'');
        cmp.set("v.msgType",'');
	}
})