htmlentity.ts

const ENTITY_REGEX = /&#x([0-9A-F]+);/gi

function entityToChar(substr: string, match: string) {
  return String.fromCharCode(parseInt(match, 16))
}

export const HtmlEntity = {
  decode: function (str: string) {
    return str.replace(ENTITY_REGEX, entityToChar)
  },
  encode: function (str: string) {
    let buf = ''
    for (let i = 0; i < str.length; i++) {
      buf += `&#x${str.charCodeAt(i).toString(16)};`
    }
    return buf
  },
}

var entity = '&#x9ad8;&#x7ea7;&#x7a0b;&#x5e8f;&#x8bbe;&#x8ba1;';
var str = '高级程序设计';
console.assert(HtmlEntity.decode(entity) === str);
console.assert(HtmlEntity.encode(str) === entity);