var code = '<script>alert(123);</script>';
$(body).append(code);
$('body').append('\<script\>alert(123)\</script\>');
const script = document.createElement('script');
script.innerText = 'alert(123)';
document.body.appendChild(script);
document.body.append(document
.createRange()
.createContextualFragment('<script>alert(123)</script>')
);