SweetAlert позволяет HTML
<script>
Swal.fire({
html: "Hello, <strong>world!</strong>"
});
</script>
hirohito
<script>
Swal.fire({
html: "Hello, <strong>world!</strong>"
});
</script><script>
// when window loades this alert pop ups
swal({
text: "Hello world!",
} );
</script>