问如果在Firebase中找不到语句变量== null？

EN

return db.ref('Global/Cuisine').once('value').then(cuisineList =>{
     console.log(`Value cuisineList --> ${JSON.stringify(cuisineList)}`);
     //print Value cuisineList --> null
     if(cuisineList == null){
         console.log(`Doesn't exists`);
         //Do stuff

     }else{
         console.log(`Exists`);
         //do stuff
     }
})

if(!cuisineList)

if(cuisineList === null)

return db.ref('Global/Cuisine').once('value').then(snapcuisineList =>{
   let cuisineList = snapcuisineList.val();
   console.log(`Valor cuisineList --> ${JSON.stringify(cuisineList)}`);
   if(cuisineList == null)
        ...