Use duplicate class name on an element?

Question

I found that there are many frameworks will check the duplicate class name before adding the new class name on the element that i think will slow down the performance.

Answer 1

Semantic UI heavily uses attribute selectors

like here

.ui.grid [class*="left floated"].column {
  margin-right: auto;
}
.ui.grid [class*="right floated"].column {
  margin-left: auto;
}

If you want margin-left and margin-right to have the auto value, you must have a duplicate of the classname segment floated (ex.

Lorem

)