distance.js

let distance = (str1, str2) => {
  let distanceTable = []
  for (let i = 0; i <= str1.length; ++i) {
    distanceTable[i] = []
    for (let j = 0; j <= str2.length; ++j) {
      distanceTable[i][j] = -1
    }
  }
  for (let i = 0; i <= str1.length; ++i) {
    distanceTable[i][0] = i
  }
  for (let i = 0; i <= str2.length; ++i) {
    distanceTable[0][i] = i
  }

  for (let i = 1; i <= str1.length; ++i) {
    for (let j = 1; j <= str2.length; ++j) {
      let cost = (str1[i - 1] === str2[j - 1] ? 0 : 1)
      distanceTable[i][j] = Math.min(
        distanceTable[i - 1][j] + 1,
        distanceTable[i][j - 1] + 1,
        distanceTable[i - 1][j - 1] + cost
      )
    }
  }
  return distanceTable[str1.length][str2.length]
}

console.log(distance("abcde", "cd"))