I can create a function in JavaScript and call it as follows:

funcaoTeste = function() 
{
	console.log('Ola funcao teste');
};

funcaoTeste();

To execute the function I need to call it funcaoTeste() , entertaining, sometimes I run into JavaScript codes where a function is executed but I do not see where it is called.

See this handy illustration example:

window.onload = function()
{
    document.getElementById('form-exemplo').onsubmit = function (event) 
    {
        if ( CPF.validate(document.getElementById('cpf').value) !== true ) 
        {
            alert("CPF invalido");
            return false;
        }
    };
};

The code above refers to this form:

<form method="post" id="form-exemplo">
    <label for="nome">Nome </label>
    <input type="text" id="nome" placeholder="Digite o nome" required>

    <label for="cep">CEP </label>       
    <input type="text" id="cep" placeholder="Digite o CEP" required pattern="\d{5}-?\d{3}">

    <label for="cpf">CPF </label>
    <input type="text" id="cpf" placeholder="Digite o CPF" required>

    <input type="submit" value="Enviar">
</form>

Note that the onload() and onsubmit() functions have been declared, but there is no call to them in script . It seems that this occurs in an automatic way that I do not know.

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