Adding values to a deserialized JSON object attribute in Javascript

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My problem is this: I am retrieving a Json object from localStorage via Javascript, and I wanted to add a value to one of these attributes, and then save the d evolta object in Storage location. However, when doing the operation: object.attribute = object.attribute + umValueNumeric; what happens is that the values are concatenated into the attribute. That is, instead of 1+1 resulting in two, the result is saved in Json as "11".

In this example below, the current account balance was 122.00 and I tried to add 8772.99.

The two zeroes you have in front is because I couldn’t format the right Pattern yet.

Just follow my code:

function processaConfirmDep(){


        var valor = document.getElementById('valorDeposito');
        var favorecido = document.getElementById('nomeFav');



            var objDep;


            var cliente = localStorage.getItem(favorecido.value);
            var clienteConta = JSON.parse(cliente);
            var agenciaFav = clienteConta.agencia;
            var contaFav = clienteConta.conta;

            objDep = {
            id : "12",
            agenciaFav : agenciaFav.value,
            contaFav : contaFav.value,
            valor : valor.value
            }
            clienteConta.saldo = clienteConta.saldo+valor.value;

            var clienteDeposito = createMyObject("DepositoLucas", [clienteConta, objDep]);

            localStorage["DepositoLucas"] = JSON.stringify(clienteDeposito);
            localStorage[clienteConta.nome] = JSON.stringify(clienteConta);

        }

Result on Storage Location. (See the "Lucas" key object, attribute "Balance"):

{"DepositoLucas":[{"nome":"Lucas","agencia":"33333","conta":"4123","saldo":"0122,008772,99"},{"id":"12","valor":"8772,99"}]}



Lucas {"nome":"Lucas","agencia":"33333","conta":"4123","saldo":"0122,008772,99"}
javascript html5 json
  • 1

    Before doing the operation. You must convert the data to the type number. You can use the function parseFloat(). Because in this way what is happening is an operation on strings. So a concatenation is made.

  • 1

    Ah, when converting the data. Remember to replace the comma (,) with a dot (.). That is: 122.00 would be 122.00

1 answer

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What is happening is that the value in the Jason object, is as string, so when trying to execute the sum, is actually concatenating. In order to be able to do the mathematical calculation, there must be a conversion using parseFloat(), follows below your code Js, corrected:

function processaConfirmDep(){

        var valor = document.getElementById('valorDeposito');
        var favorecido = document.getElementById('nomeFav');

        var objDep;

        var cliente = localStorage.getItem(favorecido.value);
        var clienteConta = JSON.parse(cliente);
        var agenciaFav = clienteConta.agencia;
        var contaFav = clienteConta.conta;

        objDep = {
        id : "12",
        agenciaFav : agenciaFav.value,
        contaFav : contaFav.value,
        valor : valor.value
        }

        var valorDepConvertido = parseFloat(valor.value);
        clienteConta.saldo = parseFloat(clienteConta.saldo)+valorDepConvertido;

        var clienteDeposito = createMyObject("DepositoLucas", [clienteConta, objDep]);

        localStorage["DepositoLucas"] = JSON.stringify(clienteDeposito);
        localStorage[clienteConta.nome] = JSON.stringify(clienteConta);

    }

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