sass extend multiple classes code example

Example 1: scss extend

.error:hover {
  background-color: #fee;
}

.error--serious {
  @extend .error;
  border-width: 3px;
}

Example 2: scss multiple classes

.container {
    background:red;
    &.desc{
       background:blue;
    }
}

/* compiles to: */
.container {
    background: red;
}
.container.desc {
    background: blue;
}