javascript - Uncaught Error: Firebase.update failed: First argument contains NaN in property 'products.quantity' -

uncaught error: firebase.update failed: first argument contains nan in property 'products.quantity'

when tried code gives error "uncaught error: firebase.update failed: first argument contains nan in property 'products.quantity'"

      import actions './actiontypes' import * db '../../firebase/database'  export function saleaction(storedata){      console.log('222222222222',storedata)     return dispatch =>{          dispatch(saleaction());         return db.database.ref('/sale').push(storedata).then((data)=>{             return db.database.ref('/products/').once('value',(snap)=>{                 var oldqty  = parseint(snap.val().quantity);                 console.log('quantityyyyyyyyyyy',oldqty)                 var newqty  = parseint(oldqty - parseint(storedata.quantity));                 return db.database.ref('/products').set(newqty,(done)=>{                     alert('successfuly')                     dispatch( saleactionsuccess(data))                 })             })          })         .catch((error)=>{             dispatch((saleactionfailed(error)))             alert('failed')         })       } }  export function saleaction(){     return{         type:actions.addsalerequest     } }  export function saleactionsuccess(data){     return{         type: actions.addsalerequestsuccess,         data     } } export function saleactionfailed(){     return{         type: actions.addsalerequestfailed     } } export default saleaction;