Method extend

src/Chain.js:223–236

* Creates a mixed alphabet by extending this chain by the given one. * @param {number[]|string|Uint8Array|Chain} alphabet Alphabet the target * should be extended by. * @return {Chain} Mixed alphabet

(alphabet)

   * @return {Chain} Mixed alphabet
   */
  extend (alphabet) {
    const key = this.getCodePoints()
    const codePoints = Chain.wrap(alphabet).getCodePoints()
    const mixedAlphabet = key.slice()
    let element
    let i = 0
    while (mixedAlphabet.length < codePoints.length && i < codePoints.length) {
      element = codePoints[i++]
      if (key.indexOf(element) === -1) {
        mixedAlphabet.push(element)
      }
    }
    return Chain.wrap(mixedAlphabet)
  }

  /**
   * Retrieves the matches when matching a string against a regular expression.