字串 => 字元實體

    function stringToEntity(str,radix){
      let arr=[]
      //返回的字元實體預設10進位制，也可以選擇16進位制
      radix=radix||0
      for(let i=0;i<str.length;i++){                               
        arr.push((!radix?'&#'+str.charCodeAt(i):'&#x'+str.charCodeAt(i).toString(16))+';')
      }
      let tmp
 
=arr.join('')
      return tmp
    }

字元實體 => 字串

    function entityToString(entity){
      let entities=entity.split(';')
      entities.pop()
      let tmp=''
      for(let i=0;i<entities.length;i++){
        let num=entities[i].trim().slice(2)
        if(num[0]==='x')//10進位制還是16進位制
          num=parseInt(num.slice(1),16);
        
 
else num=parseInt(num);
        tmp+=String.fromCharCode(num)
      }
      return tmp
    }

ES6寫法

function stringToEntity(str,radix){
  let arr=str.split('')
  radix=radix||0
  let tmp=arr.map(item=>
`&#${(radix?'x'+item.charCodeAt(0).toString(16):item.charCodeAt(0))};`).join('')
  console.log(`
 
'${str}' 轉實體為 '${tmp}'`)
  return tmp
}
function entityToString(entity){
  let entities=entity.split(';')
  entities.pop()
  let tmp=entities.map(item=>String.fromCharCode(
  item[2]==='x'?parseInt(item.slice(3),16):parseInt(item.slice(2)))).join('')
  console.log(`'${entity}' 轉字串為 '${tmp}'`)
  return tmp
}