CSS select either <thead> or <tbody> from <table>

I have the following problem. I have plenty of tables, but they all have different structure: one have <table><thead><tbody> type, while the others have <table><tbody> only.

And I need to apply css for thead (if it set in table) OR to tbody (it is set always). I shouldn't set styles for both of them, only for the first who goes after <table> tag.

So if I have

<table>
 <thead>...</thead>
   <tbody>...<tbody>
</table>

then CSS should be applied only for thead.

And vice versa if I have:

<table>
  <tbody>...</tbody>
<table>

then CSS should be applied for tbody.

I wish there was something like 'if thead is set then...'

Solution

If that is an option, you could use a hack with :first-child selector.

For example, you will select either one of them which is the first child of a <table>:

table > thead:first-child, table > tbody:first-child{
  /* properties here */
}

In this case, if a thead is present, tbody will not be the first child. Otherwise, if there is no thead, tbody will be the first child.

See it in action:

table > thead tr, /* Select the <tr> in a <thead> if present */
table > tbody:first-child tr:first-child /* Select the first <tr> in a <tbody> when the <thead> is not present */
{
  font-weight: bold;
  color: blue;
}

table{
margin-top:1em;
border: 1px solid black;
}

<table>
  <thead>
    <tr><th>This is a table with header</th></tr>
  </thead>
  <tbody>
    <tr><td>This is the body</td></tr>
  </tbody>
</table>

<table>
  <tbody>
    <tr><td>This is a table without header</td></tr>
  </tbody>
  <tbody>
    <tr><td>This is the body</td></tr>
  </tbody>
</table>