Javascript: encode(decode) html text into html entity

htmlentity.js

// encode(decode) html text into html entity
var decodeHtmlEntity = function(str) {
  return str.replace(/&#(\d+);/g, function(match, dec) {
    return String.fromCharCode(dec);
  });
};

var encodeHtmlEntity = function(str) {
  var buf = [];
  for (var i=str.length-1;i>=0;i--) {
    buf.unshift(['&#', str[i].charCodeAt(), ';'].join(''));
  }
  return buf.join('');
};

var entity = '高级程序设计';
var str = '高级程序设计';
console.log(decodeHtmlEntity(entity) === str);
console.log(encodeHtmlEntity(str) === entity);
// output:
// true
// true

htmlentity.ts

const decodeHtmlEntity = function (str: string) {
  return str.replace(/&#(\d+);/g, function (match: string, dec: number) {
    return String.fromCharCode(dec)
  })
}

const encodeHtmlEntity = function (str: string) {
  const buf = []
  for (let i = str.length - 1; i >= 0; i--) {
    buf.unshift(['&#', str.charCodeAt(i), ';'].join(''))
  }
  return buf.join('')
}

const entity = '高级程序设计';
const str = '高级程序设计';
console.log(decodeHtmlEntity(entity) === str);
console.log(encodeHtmlEntity(str) === entity);