Good morning friends, I have the following question: can you pass data from a daughter window to a parent? I already know that you can pass data from a father to a daughter through ajax, but how do you do the opposite? 
It's something like that from small to large, thank you very much ..
If the window you open belongs to your same web application, use the window.opener :
Returns a reference to the window that opened this current window.
For example in your main window:
window.open("url_ventana_de_mi_aplicacion"); // abrimos la ventana
function asignarResultados(resultado)
{
alert(resultado);
}
Then to send the data to the parent window from the other window would be:
<script>
window.opener.asignarResultado("Hola desde la otra ventana");
</script>
By variable GET with javascript
function abrirVentana() {
window.open("ventanaNueva.php?var=data", "popupId", "location=no,menubar=no,titlebar=no,resizable=no,toolbar=no, menubar=no,width=500,height=500");
}
ventanaNueva.php is the page that will process your request, and var=data is the variable with your content that you will send
for example ventanaNueva.php?dia=15&mes=12