the Real Solution:
app.clientside_callback(
“”"
function placeholder(n_clicks, value) {
window.value_to_copy = value.value;
var copyText = document.getElementById(“output4”);
if(copyText !== null){
copyText.select();
copyText.setSelectionRange(0, 99999);
document.execCommand("copy");
}
}
""",
Output("teste4", "children"),
Input("button", "n_clicks"),
State("textarea", "value"),
)