JSFiddle - React, Tailwind, and code Playground

JavaScript

var str = "...brown #fox jumped...";

var arr1 = str.match(/#([^\s]+)/g); //["#fox"]
var arr2 = str.match(/#([^\s]+)/); //["#fox", "fox"]

console.log(arr1.join(", ")); //#fox
console.log(arr2.join(", ")); //#fox, fox