Javascript help - get element by tag name

How do i make something where it displays all the elements CSS classes in one string? example,

<myelementname class='classone'></myelementname>
<myelementname class='classtwo'></myelementname>

so how could i make a string saying 'classone, classtwo'? all i need is them to be in their. doesnnt matter if theirs numbers, commas, anything. any help?

note - their will be more than two elements. i want it to automaticly display them all.

Trying to understand yr comment.
You mean this?


Example

.MyElement {
}

Please comment if incorrect answer to your question.

A true developer