Added commands.js and editDistance function

Created commands.js for command related functions. Also
added edit distance calculation for error correction.

commands.js

@@ -0,0 +1,34 @@
+// Compute the edit distance between the two given strings
+function getEditDistance(sourceString, targetString) {
+    if (sourceString.length === 0) return targetString.length;
+    if (targetString.length === 0) return sourceString.length;
+
+    let matrix = [];
+
+    // increment along the first column of each row
+    for (let i = 0; i <= targetString.length; i++) {
+        matrix[i] = [i];
+    }
+
+    // increment each column in the first row
+    for (let j = 0; j <= sourceString.length; j++) {
+        matrix[0][j] = j;
+    }
+
+    // Fill in the rest of the matrix
+    for (let i = 1; i <= targetString.length; i++) {
+        for (let j = 1; j <= sourceString.length; j++) {
+            let cost = 1;
+            if (targetString.charAt(i-1) === sourceString.charAt(j-1)) {
+                cost = 0;
+            }
+            matrix[i][j] = Math.min(matrix[i-1][j-1] + cost, // substitution
+                matrix[i][j-1] + 1, // insertion
+                matrix[i-1][j] + 1  // deletion
+            );
+        }
+    }
+    return matrix[targetString.length][sourceString.length];
+}
+
+//console.log(getEditDistance("saturday", "sunday")); //sollte 3 ergeben