cnf-barcode/src/lib/barcodes/CODE39/index.js

a barcode generator

// Encoding documentation:
// https://en.wikipedia.org/wiki/Code_39#Encoding

import Barcode from "../Barcode.js";

class CODE39 extends Barcode {
  constructor(data, options) {
    data = data.toUpperCase();

    // Calculate mod43 checksum if enabled
    if (options.mod43) {
      data += getCharacter(mod43checksum(data));
    }

    super(data, options);
  }

  encode() {
    // First character is always a *
    let result = getEncoding("*");

    // Take every character and add the binary representation to the result
    for (let i = 0; i < this.data.length; i++) {
      result += `${getEncoding(this.data[i])}0`;
    }

    // Last character is always a *
    result += getEncoding("*");

    return {
      data: result,
      text: this.text,
    };
  }

  valid() {
    return this.data.search(/^[0-9A-Z\-\.\ \$\/\+\%]+$/) !== -1;
  }
}


// All characters. The position in the array is the (checksum) value
const characters = [
  "0", "1", "2", "3",
  "4", "5", "6", "7",
  "8", "9", "A", "B",
  "C", "D", "E", "F",
  "G", "H", "I", "J",
  "K", "L", "M", "N",
  "O", "P", "Q", "R",
  "S", "T", "U", "V",
  "W", "X", "Y", "Z",
  "-", ".", " ", "$",
  "/", "+", "%", "*",
];

// The decimal representation of the characters, is converted to the
// corresponding binary with the getEncoding function
const encodings = [
  20957, 29783, 23639, 30485,
  20951, 29813, 23669, 20855,
  29789, 23645, 29975, 23831,
  30533, 22295, 30149, 24005,
  21623, 29981, 23837, 22301,
  30023, 23879, 30545, 22343,
  30161, 24017, 21959, 30065,
  23921, 22385, 29015, 18263,
  29141, 17879, 29045, 18293,
  17783, 29021, 18269, 17477,
  17489, 17681, 20753, 35770,
];

// Get the binary representation of a character by converting the encodings
// from decimal to binary
function getEncoding(character) {
  return getBinary(characterValue(character));
}

function getBinary(characterValue) {
  return encodings[characterValue].toString(2);
}

function getCharacter(characterValue) {
  return characters[characterValue];
}

function characterValue(character) {
  return characters.indexOf(character);
}

function mod43checksum(data) {
  let checksum = 0;
  for (let i = 0; i < data.length; i++) {
    checksum += characterValue(data[i]);
  }

  checksum %= 43;
  return checksum;
}

export { CODE39 };