Determine if two strings are similar in Javascript?

Question

Let's say I have two strings, is there any way to check if they are at least 90% similar?

var string1 = "theBoardmeetstoday,tomorrow51";
var string2 = "Board meets today, tomorrow";

Thanks,

Tegan

score 22 · Accepted Answer · answered Oct 14 '10 at 16:39

22

The wikipedia entry for Levenshtein distance includes a sample implementation.

answered Oct 14 '10 at 16:39

rtalbot

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Can you provide a link to the exact revision of the page with this example (in case the example is deleted from the page?) – Anderson Green Nov 24 '12 at 01:50
2

Here is the specific revision of the page (from October 14, 2010): http://en.wikipedia.org/w/index.php?title=Levenshtein_distance&oldid=384505495 – Anderson Green Nov 24 '12 at 02:04

score 12 · Answer 2 · edited Jan 30 '14 at 11:25

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jsdifflib is a JavaScript port of Python's excellent difflib library.

It has a function ratio() which "return[s] a measure of the sequences’ similarity as a float in the range [0, 1]."

edited Jan 30 '14 at 11:25

cemerick

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answered Oct 14 '10 at 16:35

RichieHindle

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score 5 · Answer 3 · answered Sep 27 '18 at 15:53

Also consider Dice's Coefficient which is considered "mostly better" than the Levenshtein distance by the creator of the string-similarity github repo and its corresponding npm module.

Usage from its docs:

var stringSimilarity = require('string-similarity');

var similarity = stringSimilarity.compareTwoStrings('healed', 'sealed'); 

var matches = stringSimilarity.findBestMatch('healed', ['edward', 'sealed', 'theatre']);

score 4 · Answer 4 · edited Oct 26 '12 at 17:17

String.levenshtein (a plugin MooTools)

check it out: http://mootools.net/forge/p/string_levenshtein

GitHub: https://github.com/thinkphp/String.levenshtein

This method calculates Levenshtein distance between two strings. In information theory and computer science, the Levenshtein distance is a metric for measuring the amount of difference between two sequences (called edit distance). The Levenshtein distance between two strings is given by minimum number of operations needed to transform one string into another given string, where possible operations are insertion, deletion, or substitution of a single character.

The Levenshtein distance algorithm has been used in:

Spell checking
Speech recognition
DNA analysis
plagiarism detection

here is the same code but without mootools dependency - https://gist.github.com/luchaninov/a5730c453129ae159dfc — luchaninov, Aug 06 '15 at 17:40

score 0 · Answer 5 · answered Mar 31 '21 at 22:21

piggybacking on other people's answers, I wrote a simple js function stringsAreSimilar to do this:

// https://github.com/thinkphp/String.levenshtein/blob/master/Source/String.levenshtein.js

function getStringDifference(stringA, stringB) {
  var cost = [],
    str1 = stringA,
    str2 = stringB,
    n = str1.length,
    m = str2.length,
    i, j;

  var minimum = function (a, b, c) {
    var min = a;
    if (b < min) {
      min = b;
    }
    if (c < min) {
      min = c;
    }
    return min;
  };

  if (n == 0) {
    return;
  }
  if (m == 0) {
    return;
  }

  for (var i = 0; i <= n; i++) {
    cost[i] = [];
  }

  for (i = 0; i <= n; i++) {
    cost[i][0] = i;
  }

  for (j = 0; j <= m; j++) {
    cost[0][j] = j;
  }

  for (i = 1; i <= n; i++) {

    var x = str1.charAt(i - 1);

    for (j = 1; j <= m; j++) {

      var y = str2.charAt(j - 1);

      if (x == y) {

        cost[i][j] = cost[i - 1][j - 1];

      } else {

        cost[i][j] = 1 + minimum(cost[i - 1][j - 1], cost[i][j - 1], cost[i - 1][j]);
      }

    } //endfor

  } //endfor

  return cost[n][m];
}

function stringsAreSimilar(stringA, stringB) {
  var difference = getStringDifference(stringA, stringB);
  debugConsoleLog("stringA" + stringA);
  debugConsoleLog("stringB" + stringB);
  debugConsoleLog("difference" + difference);
  
  return difference < 10;
}

var string1 = "theBoardmeetstoday,tomorrow51";
var string2 = "Board meets today, tomorrow";

if(similar) {
    console.log("they are similar");
} else {
    console.log("they are not similar");
}

score 0 · Answer 6 · answered Jan 19 '22 at 14:37

So I was trying to do this last year. I read that Levenshtein distance is the solution for this purpose the OP asked here.

I saw a code from a thread and was not given much upvotes. Maybe because of its time complexity (having a forloop inside a forloop). I tried and it seem to work for me. The function returns a score wherein 0 is a great match on the other hand a higher score means deviating from a close match. Ill share and maybe someone can extend it or explain it better:

function editDistance(s1, s2) {
    s1 = s1.toLowerCase();
    s2 = s2.toLowerCase();

    var costs = new Array();
    for (var i = 0; i <= s1.length; i++) {
        var lastValue = i;
        for (var j = 0; j <= s2.length; j++) {
            if (i == 0) costs[j] = j;
            else {
                if (j > 0) {
                    var newValue = costs[j - 1];
                    if (s1.charAt(i - 1) != s2.charAt(j - 1))
                        newValue =
                            Math.min(Math.min(newValue, lastValue), costs[j]) +
                            1;
                    costs[j - 1] = lastValue;
                    lastValue = newValue;
                }
            }
        }
        if (i > 0) costs[s2.length] = lastValue;
    }
    return costs[s2.length];
}

Good luck and share your thoughts on this - would be awesome! Cheers!

Determine if two strings are similar in Javascript?

6 Answers6