JSFiddle - React, Tailwind, and code Playground

JavaScript

function numericEntityToChar(s) {
    var re = /&#(\d+);/g,
        ret = "", match;
    while (match = re.exec(s)) {
        ret += String.fromCharCode(match[1]);
    }
    return ret;
}

var str = "登入";
console.log(numericEntityToChar(str));