hamstrings

index.js

function FromRight(str1, str2) {
  var longest, tmpshortest, shortest;
  if(str1.length != str2.length) {
    if(str1.length > str2.length) {
      longest = str1;
      tmpshortest = str2;
    } else {
      longest = str2;
      tmpshortest = str1;
    }

    shortest = "\0".repeat(longest.length - tmpshortest.length) + tmpshortest;
  } else {
    longest = str1;
    shortest = str2;
  }
  return FromLeft(longest, shortest);
}
function FromLeft(str1, str2) {
  var longest, tmpshortest, shortest, max, score, diff, percent;
  if(str1.length != str2.length) {
    if(str1.length > str2.length) {
      longest = str1;
      tmpshortest = str2;
    } else {
      longest = str2;
      tmpshortest = str1;
    }

    shortest = tmpshortest + "\0".repeat(longest.length - tmpshortest.length);
  } else {
    longest = str1;
    shortest = str2;
  }

  max = longest.length;

  score = (function (longest, shortest) {
    var i, result;

    i = longest.length;
    result = 0;

    while(i--) {
      result += Number(longest[i] == shortest[i]);
    }
    return result;
  })(longest, shortest);

  return {
    score: score,
    percent: (score/max),
    diff: (max-score),
    max: max
  };
};

function BestFirstMatch(str1, str2) {
  var longest, shortest, max, score, diff, percent;
  if(str1.length != str2.length) {
    if(str1.length > str2.length) {
      longest = str1;
      shortest = str2;
    } else {
      longest = str2;
      shortest = str1;
    }
  } else {
    longest = str1;
    shortest = str2;
  }

  max = longest.length;

  var searchresults = (function(longest, shortest) {
    var i = longest.length - shortest.length;
    var testlength = shortest.length;
    var best = {score: 0};
    var iscore = {score: 0};
    var besti = i;
    while(i--) {
      iscore = FromLeft(longest.slice(i, i+testlength), shortest);
      if(iscore.score >= best.score) {
        best = iscore;
        best.index = i;
      }
    }
    return best;
  })(longest, shortest);

  return searchresults;
};

module.exports = {
  BestFirstMatch: BestFirstMatch,
  FromLeft: FromLeft,
  FromRight: FromRight
};

tests.js

var assert = require('assert')
var s = require('./index.js');

(function() {
  //{ score: 3, percent: 0.42857142857142855, diff: 4, max: 7 }
  var result = s.FromLeft("abc", "abcdefg");

  assert.eq(result.score, 3);
  assert.eq(result.diff, 4);
  assert.eq(result.max, 7);
})();

(function() {
  //{ score: 0, percent: 0, diff: 7, max: 7 }
  var result = s.FromRight("abc", "abcdefg");

  assert.eq(result.score, 0);
  assert.eq(result.diff, 0);
  assert.eq(result.max, 7);
})();

(function() {
  //{ score: 3, percent: 0.75, diff: 1, max: 4, index: 4 }
  var result = s.BestFirstMatch("cdxf", "_fabcdefg04ma");

  assert.eq(result.score, 3);
  assert.eq(result.diff, 1);
  assert.eq(result.max, 4);
  assert.eq(result.index, 4);
})();

(function() {
  //{ score: 4, percent: 1, diff: 0, max: 4, index: 4 }
  var result = s.FromLeft("cdef", "_fabcdefg04ma");

  assert.eq(result.score, 4);
  assert.eq(result.diff, 0);
  assert.eq(result.max, 4);
})();