<div class="form-group">
  <label class="col-md-4 control-label" for="textinput">Valor do saque</label>
  <div class="col-md-2">
  <input id="textinput" name="textinput" value="" type="text" placeholder="R$ 00,00" class="form-control input-md" required="">
 </div>
</div>

<button onclick="enviar()">Confirmar</button>

<script type="text/javascript">
    function enviar(){
        var valor = document.getElementById("textinput").value;
        alert(valor);

        return false;
    }
</script>

<button id="confirmar">Confirmar</button>

<script type="text/javascript">
    $('body').on('click','#confirmar',function(){
        var valor = $('#textinput').val();
        alert(valor);

        return false;
    })
</script>