function compSetting()
{
myItems = app.project.selection;
if (! myItems)
{
alert(“You have to select some comps in the Project Pannel!”);
return;
}
else
{
for (var i = 0; i < myItems.length; i ++)
{
myItems[i].duration = 20
}
}
}

compSetting();

将代码粘贴新建text 中 然后后缀名改成jsx  在ae软件中脚本调用中打开这个文件即可