// your code goes here
const s = "あ い&う え"
let out = s.replace(/&#(\d{1,5});/g, (...matches) => String.fromCharCode(parseInt(matches[1])))
.split(/\s| /).join(" ")
console.log(out)
Ly8geW91ciBjb2RlIGdvZXMgaGVyZQpjb25zdCBzID0gIuOBgiYjMTYwO+OBhCYjMzg744GG44CA44GIIgoKbGV0IG91dCA9IHMucmVwbGFjZSgvJiMoXGR7MSw1fSk7L2csICguLi5tYXRjaGVzKSA9PiBTdHJpbmcuZnJvbUNoYXJDb2RlKHBhcnNlSW50KG1hdGNoZXNbMV0pKSkKCQkJLnNwbGl0KC9cc3zjgIAvKS5qb2luKCIgIikKCmNvbnNvbGUubG9nKG91dCk=