ncr-decode/src/index.js

A Tool to decode numeric character reference(NCR)

/**
 * numerric character reference(NCR) to raw chinese
 * @param {string} str
 */
function ncrDecode(str) {
  str = str.replace(/(&#)(\d{1,6});/gi, function ($0) {
    return String.fromCharCode(
      parseInt(escape($0).replace(/(%26%23)(\d{1,6})(%3B)/g, '$2'))
    )
  })
  str = str.replace(/(&#x)(\w{1,4});/gi, function ($0) {
    return String.fromCharCode(
      parseInt(escape($0).replace(/(%26%23x)(\w{1,4})(%3B)/g, '$2'), 16)
    )
  })
  return str
}
/**
 * special encode string to NCR
 * @param {string} str
 */
function str2NCR(str) {
  if (!typeof str === 'string') return ''
  let reg = /(#x?)/g
  if (!reg.test(str)) return str
  str = str.replace(reg, ';&$&')
  str = str.slice(1)
  str += ';'
  return str
}
/**
 * string to NCR string
 * @param {string} str
 * @param {number} radix 10 or 16 default is 10
 * @returns {string} NRC string
 */
function ncrEncode(str, radix = 10) {
  if (!str || typeof str !== 'string') return ''
  if ([10, 16].indexOf(radix) === -1) {
    throw new Error(`Unsupported radix ${radix}, use 10 or 16 instead`)
  }
  let result = ''
  for (let char of str) {
    let codePoint = char.codePointAt().toString(radix)
    result += `&#${radix === 16 ? 'x' : ''}${codePoint};`
  }
  return result
}

function checkNCR(str) {
  let reg = /&#x?/
  return reg.test(str)
}

/**
 * decode delphi .dfm file encoded chinese
 * @param {string} str
 */
function dfmDecode(str) {
  return checkNCR(str) ? ncrDecode(str) : ncrDecode(str2NCR(str))
}

exports.ncrDecode = ncrDecode
exports.decode = ncrDecode
exports.ncrEncode = ncrEncode
exports.encode = ncrEncode
exports.dfmDecode = dfmDecode