Thunderbird 68.4.1: How to check if a message is marked as "junk"?

Question

In some self-written add-on for Thunderbird I have to check if some message is marked as "junk".

In Thunderbird 68.3 the following code worked perfectly:

isJunk = false;
for(i = 0; i < message.tags.length; i++)
{
    if(message.tags[i] == "junk") isJunk = true;
}

Unfortunately, the tags array seems always to be empty in Thunderbird 68.4.1 so the code above does not work any longer.

How can I check if some message is marked as "junk" in newer Thunderbird versions?