boleto-barcode-svg/src/itf.js

Generate brazilian boleto barcode in SVG

/**
 * Encodes a base-10 number into its Interleaved 2 of 5 (ITF) representation
 *
 * @param {String} number The number to be encoded
 * @return {String} The input number encoded into its ITF representation
 *
 * @example
 * // Returns "111121121111222121121112211222111112111122211121122211211"
 * ITF.encode('1234567890');
 */
export function itf(number) {
  return START + number.match(/(..?)/g).map(interleavePair).join("") + STOP
}

const START = "1111" // Representation of Start portion of the barcode
const STOP = "211" // Representation of Stop portion of the barcode

// Representations of each decimal digit
const WEIGHTS = [
  "11221", // 0
  "21112", // 1
  "12112", // 2
  "22111", // 3
  "11212", // 4
  "21211", // 5
  "12211", // 6
  "11122", // 7
  "21121", // 8
  "12121" // 9
]

/**
 * Converts a pair of digits into their ITF representation and interleave them
 *
 * @param {String} pair The pair to be interleaved
 * @return {String} The input pair encoded into its ITF representation
 *
 * @example
 * // Returns "1211212112"
 * ITF.interleavePair('01');
 */
function interleavePair(pair) {
  const black = WEIGHTS[Math.floor(pair / 10)]
  const white = WEIGHTS[pair % 10]

  let p = ""

  for (let i = 0; i < 5; i += 1) {
    p += black[i]
    p += white[i]
  }

  return p
}