Fetch doctype child table data to another doctype

Try to fetch doctype child table field data to another doctype using frappe.db.get_value
it doesn’t work but no errors !

JS code:

frappe.ui.form.on(“doctype A”,{field1:function(frm){
frappe.call({
method:“frappe.db.get_value”,
args: {
doctype:“childtable doctype b”,
filters:{parent:frm.doc.field1,field2:frm.doc.field2},
fieldname: “f1”
},
callback: function(r){
frappe.model.set_value(“f1”, r.f1);

});
}
})

You got the solution ?

/any update here ?