--- /dev/null
+var makeString = require('./helper/makeString');
+
+/**
+ * Based on the implementation here: https://github.com/hiddentao/fast-levenshtein
+ */
+module.exports = function levenshtein(str1, str2) {
+ 'use strict';
+ str1 = makeString(str1);
+ str2 = makeString(str2);
+
+ // Short cut cases
+ if (str1 === str2) return 0;
+ if (!str1 || !str2) return Math.max(str1.length, str2.length);
+
+ // two rows
+ var prevRow = new Array(str2.length + 1);
+
+ // initialise previous row
+ for (var i = 0; i < prevRow.length; ++i) {
+ prevRow[i] = i;
+ }
+
+ // calculate current row distance from previous row
+ for (i = 0; i < str1.length; ++i) {
+ var nextCol = i + 1;
+
+ for (var j = 0; j < str2.length; ++j) {
+ var curCol = nextCol;
+
+ // substution
+ nextCol = prevRow[j] + ( (str1.charAt(i) === str2.charAt(j)) ? 0 : 1 );
+ // insertion
+ var tmp = curCol + 1;
+ if (nextCol > tmp) {
+ nextCol = tmp;
+ }
+ // deletion
+ tmp = prevRow[j + 1] + 1;
+ if (nextCol > tmp) {
+ nextCol = tmp;
+ }
+
+ // copy current col value into previous (in preparation for next iteration)
+ prevRow[j] = curCol;
+ }
+
+ // copy last col value into previous (in preparation for next iteration)
+ prevRow[j] = nextCol;
+ }
+
+ return nextCol;
+};