A Common-Sense Guide to Data Structures and Algorithms in JavaScript, Volume 1

Word Builder

The next example is an algorithm that collects every combination of two-character strings built from an array of single characters. For example, given the array ["a", "b", "c", "d"], we’d return a new array containing the following string combinations:

[
  'ab', 'ac', 'ad', 'ba', 'bc', 'bd',
  'ca', 'cb', 'cd', 'da', 'db', 'dc'
]

Following is an implementation of this algorithm. Let’s see if we can figure out its Big O efficiency:

function wordBuilder(array) {
  const collection = [];

  for (const [indexI, valueI] of array.entries()) {
    for (const [indexJ, valueJ] of array.entries()) {
      if (indexI !== indexJ) {
        collection.push(valueI + valueJ);
      }
    }
  }

  return collection; ...