How to pass the value of a variable to an Hidden input?

Question

How can I pass the value from a Javascript variable to a input hidden ?

Answer 1

It would be good if you put some code but basically with jquery would be like this:

$("#botao").click(function(){
var minhaVariavel="valor";
  alert("Antes de atribuir o valor:"+$("input[name='campoInvisivel']").val());
$("input[name='campoInvisivel']").val(minhaVariavel);
alert("Depois de atribuir o valor:"+$("#campoInvisivel").val());
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="hidden" name="campoInvisivel" id="campoInvisivel">
<input type="button" value="Colocar Valor com Jquery" id="botao">

Here the example only with Javascript, remembering that the alert are only for demonstration, the line on which you pass the value to the input is that document.getElementById("campoInvisiveljs").value=minhaVariavel;. Below is the complete code

// Aqui é só com js
function passarValor(){
var minhaVariavel="valor";
alert("Antes de passar o valor:"+ document.getElementById("campoInvisiveljs").value);
document.getElementById("campoInvisiveljs").value=minhaVariavel;
alert("Depois de passar o valor:"+document.getElementById("campoInvisiveljs").value);
}

   <input type="hidden" name="campoInvisiveljs" id="campoInvisiveljs">
   <input type="button" value="Colocar Valor com Java Script" id="botao" onClick="passarValor();">

Answer 2

With javascript just assign the value to the attribute value:

var variavel = ["a", "b", "c"];
document.getElementById("input_hidden_id").value = variavel.join("");

Example:

    var variavel = ["a", "b", "c"];
    document.getElementById("input_hidden_id").value = variavel.join("");

    function verValor() {
      document.write(document.getElementById("input_hidden_id").value);
    }

<input id="input_hidden_id" type="hidden" value="123" />
<button onclick="verValor()">Ver Valor</button>

Answer 3

You can do it like this:

var dados = ['eu', 'tu', 'ele'];
var input = document.getElementById('escondido');
input.value = JSON.stringify(dados);

<input type="hidden" id="escondido" />

Thus the input will receive as value a JSON that can easily be converted into array on the server or when reading its value.