var promise = $A.enqueueAction(action);
promise.then(function(result){
   // Do something
});

callAction : function( component, actionName, params ) {

    var helper = this;

    var p = new Promise( function( resolve, reject ) {

        helper.showSpinner( component );

        var action = component.get( actionName );

        if ( params ) {
            action.setParams( params );
        }

        action.setCallback( helper, function( response ) {

            helper.hideSpinner( component );

            if ( component.isValid() && response.getState() === 'SUCCESS' ) {

                resolve( response.getReturnValue() );

            } else {

                console.error( 'Error calling action "' + actionName + '" with state: ' + response.getState() );

                reject( response.getError(), response.getState() );

            }
        });

        $A.enqueueAction( action );

    });

    return p;
},

someMethod : function( component, event, helper ) {

    var helper = this;

    helper.callAction( component, 'c.someApexMethod', {

        'someParam' : component.get( 'v.someAttribute' )

    }).then( $A.getCallback( function( data ) {

        component.set( 'v.anotherAttribute', data );

    })).catch( $A.getCallback( function( errors, state ) {

        helper.logActionErrors( component, errors );

    }));

}

component.lax.enqueue('c.getParentValue')
  .then(parentValue => {
      component.set('v.parentValue', parentValue);
      return component.lax.enqueue('c.getDependentValue', { parentValue: parentValue });
  })
  .then(dependentValue => {
      component.set('v.dependentValue', dependentValue);
  });