Sample Code:
Component:
<aura:component implements="flexipage:availableForAllPageTypes,force:appHostable" >
<lightning:recordEditForm recordId="0036A00000QAY0CQAX" objectApiName="Contact" onsuccess="{!c.callSuccess}">
<lightning:messages />
<lightning:inputField fieldName="FirstName" />
<lightning:inputField fieldName="LastName" />
<lightning:inputField fieldName="Email" />
<lightning:button class="slds-m-top_small" variant="brand" type="submit" name="update" label="Update"/>
</lightning:recordEditForm>
</aura:component>
Controller:
({
callSuccess : function(component, event, helper) {
var params = event.getParams();
alert(params.response.id);
}
})
Output: