Check the value of an element and take action

I would like a function that checks if some fields of the form have been filled out and if true it would execute a code of mine, if false it would do nothing.

In short, I would like to know how I check the fields, the code that will be executed, I already have it ready.

HTML of the fields I want to check if they have been filled out:

<!-- verifica select -->

<div class="form-group pmd-textfield col-md-4">
  <label for="InqueritoCircunscricaoPolicial" class="control-label cssPerguntas espacamentoLabels">
    <strong>1.1</strong> Circunscrição policial
  </label>
  <select asp-for="InqueritoModel.COD_INQUERITO_CIRCUNSCRICAO_POLICIAL "
          asp-items="Model.ListCircunscricao"
          id="InqueritoCircunscricaoPolicial"
          class="select-codigo"
          onchange="mostrarOutroDeCombo(this, 'DSC_OUTRO_INQUERITO_CIRCUNSCRICAO_POLICIAL')">
    <option value="">Selecione a circunscrição</option>
  </select>
</div>

<!-- verifica input -->

<div class="form-group pmd-textfield col-sm-3">
  <label for="NumeroDaOcorrencia" class="control-label cssPerguntas espacamentoLabels">
    <strong>1.3</strong> Número da ocorrência
  </label>
  <input class="form-control" id="NumeroDaOcorrencia" maxlength="1000" placeholder="N° da ocorrência"
         asp-for="InqueritoModel.NumeroDaOcorrencia"
         type="text">
</div>

<!-- verifica input -->

<div class="form-group pmd-textfield col-sm-3">
  <label for="DataDaInstauracao" class="control-label cssPerguntas espacamentoLabels">
    <strong>1.9</strong> Data da instauração
  </label>
  <input class="form-control" id="DataDaInstauracao" min="1900-01-01"
         asp-for="InqueritoModel.DataDaInstauracao"
         type="date">  
</div>

Answer

verifyonClick = () => {
var first = document.getElementById("InqueritoCircunscricaoPolicial")
var second = document.getElementById("NumeroDaOcorrencia")
var third = document.getElementById("DataDaInstauracao")
if(first.value && second.value && third.value)
alert("Value exist in every input")
else
alert("Please enter value in all fields")
}
<!-- verifica select -->

<div class="form-group pmd-textfield col-md-4">
  <label for="InqueritoCircunscricaoPolicial" class="control-label cssPerguntas espacamentoLabels">
    <strong>1.1</strong> Circunscrição policial
  </label>
  <select asp-for="InqueritoModel.COD_INQUERITO_CIRCUNSCRICAO_POLICIAL "
          asp-items="Model.ListCircunscricao"
          id="InqueritoCircunscricaoPolicial"
          class="select-codigo"
          onchange="mostrarOutroDeCombo(this, 'DSC_OUTRO_INQUERITO_CIRCUNSCRICAO_POLICIAL')">
    <option value="">Selecione a circunscrição</option>
  </select>
</div>

<!-- verifica input -->

<div class="form-group pmd-textfield col-sm-3">
  <label for="NumeroDaOcorrencia" class="control-label cssPerguntas espacamentoLabels">
    <strong>1.3</strong> Número da ocorrência
  </label>
  <input class="form-control" id="NumeroDaOcorrencia" maxlength="1000" placeholder="N° da ocorrência"
         asp-for="InqueritoModel.NumeroDaOcorrencia"
         type="text">
</div>

<!-- verifica input -->

<div class="form-group pmd-textfield col-sm-3">
  <label for="DataDaInstauracao" class="control-label cssPerguntas espacamentoLabels">
    <strong>1.9</strong> Data da instauração
  </label>
  <input class="form-control" id="DataDaInstauracao" min="1900-01-01"
         asp-for="InqueritoModel.DataDaInstauracao"
         type="date">  
</div>

<div>
<button onclick="verifyonClick()"> submit </button>
</div>