JavaScript: Letter combinations of a number

Last update on April 22 2023 12:19:19 (UTC/GMT +8 hours)

JavaScript Function: Exercise-13 with Solution

A string consists of digits ranging from 2 to 9, inclusive. Write a JavaScript program to get all possible letter combinations that represent the number using recursion.

Letter Combination:
1: 'abc',
2: 'def',
3: 'ghi',
4: 'jkl',
5: 'mno',
6: 'pqr',
7: 'stu',
8: 'vwx'
9: 'yz'

Test Data:
("12") -> ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"]
("9") -> ["y", "z"]

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Letter combinations of a number</title>
</head>
<body>

</body>
</html>

JavaScript Code:

const test = (digits) => {
  const length = digits?.length
  const result = []
  if (!length) {
    return result
  }
  const digit_Map = {
    1: 'abc',
    2: 'def',
    3: 'ghi',
    4: 'jkl',
    5: 'mno',
    6: 'pqr',
    7: 'stu',
    8: 'vwx',
    9: 'yz'
  }

  const letter_combinations = (index, combination) => {
    let letter
    let letterIndex
    if (index >= length) {
      result.push(combination)
      return
    }
    const digit = digit_Map[digits[index]]
    letterIndex = 0
    while ((letter = digit[letterIndex++])) {
      letter_combinations(index + 1, combination + letter)
    }
  }
  letter_combinations(0, '')
  return result
}
console.log(test("12"))
console.log(test("9"))

Output:

["ad","ae","af","bd","be","bf","cd","ce","cf"]
["y","z"]

Flowchart:

Flowchart: JavaScript recursion function- Letter combinations of a number.

Live Demo:

See the Pen javascript-recursion-function-exercise-13 by w3resource (@w3resource) on CodePen.

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