Properly escape strings before converting to RegExp pattern.

package.json

@@ -2,7 +2,7 @@
   "name": "striff",
   "description": "Real simple string diffing.",
   "author": "Alex MacArthur (https://macarthur.me)",
-  "version": "1.0.1",
+  "version": "1.0.2",
   "main": "dist/index.umd.js",
   "module": "dist/index.es.js",
   "types": "dist/index.d.ts",

src/index.test.ts

@@ -7,6 +7,13 @@ it("Correctly diffs when strings are identical.", () => {
   expect(removed).toHaveLength(0);
 });
 
+it("Strings are RegEx-escaped", () => {
+  const { added, removed } = striff("Hi?", "Hi!");
+
+  expect(removed).toEqual([{ value: "?", index: 2 }]);
+  expect(added).toEqual([{ value: "!", index: 2 }]);
+});
+
 describe("characters are added", () => {
   it("Correctly diffs when characters are added to end.", () => {
     const { added, removed } = striff("abc", "abcd");

src/index.ts

@@ -11,7 +11,9 @@ const getDiff = (partsArr: Character[][], arr1: Character[], arr2: Character[])
 
   partsArr.forEach((part: Character[]) => {
     let partString = fromCharacters(part);
-    let pattern = new RegExp(partString);
+
+    // One day, `RegExp.replace` will hopefully be built-in.
+    let pattern = new RegExp(partString.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'));
 
     // If this little thing matches ANY part of the string, it's in.
     let result = pattern.exec(str2);