add class to $(el).contents()

Question

hello,
I've this:

var headers = $('h1, h2, h3').contents();
for(var i=0; i < Object.keys(headers).length-2; i++) {
if(headers[i].data) { // security
var d = headers[i].data;
var headerClass = d.replace(' ','-').toLowerCase()+'-'+i;
// here is my question : how to set the class headerClass to my headers[i] ?
}
}

Answer 1

header[i].addClass(headerClass);

Answer 2

Toni Isotalo `headers[i].addClass is not a function`
I already tried ^^
And for
headers[i].parentElement.classList.add = headerClass;
I dont have error but any header have class
If I remove the .parentElement I've same error as above

Answer 3

then it is
$(headers[i]).addClass(headerClass);