Argh, Jarek was quicker than me ;-)
I’m not sure, if this is a good solution, but for me this one works too:
app.scriptPreferences.userInteractionLevel = UserInteractionLevels.interactWithAll;
if ( !(app.selection.length == 1 && app.selection[0].constructor.name == "TextFrame" ) ) { alert( "Check your selection!" ); exit();
}
else { var curSel = app.selection[0];
}
var firstChar = curSel.characters[0];
if ( firstChar.textFrames.length == 1 || firstChar.tables.length == 1 ) {
alert( "true" );
}
else { alert( "false" );
}