fast-protocol/tests/parseNumber.js

FAST streaming protocol for Node.js (Encoder/Decoder for Javascript) (FAST protocol version 1.1)

var Long = require('long')


//[ "+" | "-" ] digit+ [ "." digit+ ]
//[ "+" | "-" ] digit [ "." digit+ ] "e" [ "+" | "-" ] digit+

function parseDecimal(str) {
  if (!str) return undefined
  // [1] SIGN
  // [2] + [4] MANTISSA
  // [6] EXPONENT
  var matches = str.match(/^([+-])?(\d+)?(\.)?(\d*)?(e([+-]?\d+))?$/)

  var sign = matches[1] != null ? matches[1] : '+'
  var pre = matches[2] != null ? matches[2] : ''
  var post = matches[4] != null ? matches[4].replace(/0*$/, '') : ''

  var mantissa = Long.fromString(pre.concat(post)).multiply(sign == '-' ? Long.NEG_ONE : Long.ONE)
  var exponent = matches[6] != null ? Number(matches[6]) - post.length : 0 - post.length
  return {m: mantissa.toString(10), e: exponent}
}

console.log('\n')
console.log('Parse number:', process.argv[2], 'result:', parseDecimal(process.argv[2]))