Implementation of Knuth-Morris-Pratt string search algorithm in JavaScript

KMP.js

// See notes at vickon.netlify.com/notes/algorithms-and-data-structures-day-3
let = longestPrefixSuffix => {
  let table = new Array(pattern.length)
  let pointer = 0
  table[0] = 0

  for (let i = 1; i < pattern.length; i++) {
    while (pointer > 0 && pattern.charAt(i) !== pattern.charAt(pointer)) {
      pointer = table[pointer - 1]
    }

    if (pattern.charAt(i) === pattern.charAt(pointer)) {
      pointer++
    }
    table[i] = pointer
  }
  return table
}

let match = (text, pattern) => {
  let prefixes = longestPrefixSuffix(pattern),
    matches = []

  let j = 0,
    i = 0

  while (i < text.length) {
    if (text.charAt(i) === pattern.charAt(j)) {
      i++
      j++
    }

    if (j === pattern.length) {
      matches.push(i - j)
      j = prefixes[j - 1]
    } else if (text.charAt(i) !== pattern.charAt(j)) {
      if (j !== 0) {
        j = prefixes[j - 1]
      } else {
        i++
      }
    }
  }

  return matches
}