str = "/&fff7321вв/;/jjj123;gggg456".replace()
alert("/&fff7321вв/;/jjj123;gggg456".replace(/\d+/,'вот_они'))
alert("/&fff7321вв/;/jjj123;gggg456".match(/\d+/))
<script> str = "/&fff7321вв/;/jjj123;gggg456".replace(/(?<=\d+[\D]+)\d+/g, '') document.write(str) </script>
'вот_они'
''
function replace(str) { let n = 0; return str.replace(/\d+/g, m => n++ ? '' : m); } alert(replace("/&fff7321вв/;/jjj123;gggg456"));