JSFiddle - React, Tailwind, and code Playground

HTML

<div id="split"></div>
<div id="replace"></div>

JavaScript

var str = "a1 a2 a3 a4 a5 (80)";

var str_split = str.split(' (');
var str_replace = str_split[0];
document.getElementById("split").innerHTML = str_replace;

var str_replace2 = str.replace(/ \([0-9]+\)/, "");
document.getElementById("replace").innerHTML = str_replace2;