typenshtein

A weighted levenshtein that takes typiness into consideration.

Typiness is the relative quality of being a typo. In lay terms, this means that a character that is closer to another in a hypothetical keyboard has more typiness relative to the other that one that is distant.

A typo is when a creature with the capacity of writing potencially correct words – typically humans – fails to do so because its members employed in that task – typically fingers – do not perform their function correctly, either by a mismatch between their central nervous system signals and the member motricity execution or simply because they are using a keyboard that they are not used to – typically Swedish –, so that their "muscle memory" fails to "remember" the right moves and end up typing one or more wrong characters. The wrongly typed characters statistically tend to be physically close to the originally intended character, and a proper detection of typos needs to take that into consideration.

Typos are normally not intentional, but this library can detect also intentional ones – there's no way to distinguish them without mind reading, which might be possible in the near future.

Detecting typos is an important thing to do because a typo can, for instance, prevent the proper delivery of a vital email or change the meaning of an intended message from "do you have a small unit of time to help me?", like in "do you have a sec?" to "were you born in a determined gender?", like in "do you have a sex?" (or any other interpretation of that sentence). This is just one example of a possible misunderstanding, but they may be harmful enough to end marriages and even cause global wars.

In practice though, this library just calculates the distance of two points in a cartesian plain.

Usage:

const { typenshtein, regularKeyboard } = require('typenshtein')

const typenshteinForRegularKeyboard = typenshtein(regularKeyboard)

typenshteinForRegularKeyboard('aaa', 'aaa') // 0 - precise
typenshteinForRegularKeyboard('aaa', 'sss') // 0 - very close, certainly typo
typenshteinForRegularKeyboard('aaa', 'www') // 1.50...4 - not so much
typenshteinForRegularKeyboard('aaa', 'ppp') // 2.9634... - far away

typenshteinForRegularKeyboard('...', '///') // 3 - not in keyboard...

// your own custom keyboard
const { typenshtein } = require('typenshtein')

const typenshteinForMyKeyboard = typenshtein({
  'ä': [0, 0],
  'β': [0, 1],
  ...
})

// actual real world use case
typenshteinForRegularKeyboard('gmail.com', 'gnail.com') // 0
typenshteinForRegularKeyboard('gmail.com', 'gbail.com') // 0.75

// the regular levenshtein doesn't distinguish both cases
levenshtein('gmail.com', 'gnail.com') // 1
levenshtein('gmail.com', 'gbail.com') // 1

Custom keyboards

As shown in the example above, you can create your own keyboard. A keyboard is just a map – an object –, with the characters as keys, and a vector: an array with 2 items, where the first represents the row of the character in the keyboard and the second represents the column. For instance, in a regular qwerty keyboard, q would be [0, 0], w would be [0, 1] and so on. a, being in the next row would be [1, 0].

The name

Typenshtein can be a portmanteau of "typo" and "levenshtein". It can also be a person who is influenced both by Russell's type theory and Ludwig Wittgenstein, usually not known as Typenshteinians.