Freeze Context object

Author: slevithan

README.md

@@ -10,7 +10,7 @@ Tiny utilities shared by the [`regex`](https://github.com/slevithan/regex) libra
 
 ### `Context`
 
-Regex syntax context object with the following properties:
+Frozen object with the following properties for tracking regex syntax context:
 
 - `DEFAULT` - Base context.
 - `CHAR_CLASS` - Character class context.

spec/utilities-spec.js

@@ -1,5 +1,22 @@
 import {Context, execUnescaped, forEachUnescaped, getGroupContents, hasUnescaped, replaceUnescaped} from '../src/index.js';
 
+describe('Context', () => {
+  it('should not allow modifying property values', () => {
+    const original = Context.DEFAULT;
+    try {
+      Context.DEFAULT = null;
+    } catch (e) {}
+    expect(Context.DEFAULT).toBe(original);
+  });
+
+  it('should not allow adding properties', () => {
+    try {
+      Context.NEW = 'NEW';
+    } catch (e) {}
+    expect('NEW' in Context).toBeFalse();
+  });
+});
+
 describe('replaceUnescaped', () => {
   it('should replace all with string replacement in all contexts', () => {
     expect(replaceUnescaped(String.raw`.\.\\.\\\.[[\.].].`, '\\.', '~')).toBe(String.raw`~\.\\~\\\.[[\.]~]~`);

src/index.js

@@ -1,7 +1,8 @@
-export const Context = {
+// Constant properties for tracking regex syntax context
+export const Context = Object.freeze({
   DEFAULT: 'DEFAULT',
   CHAR_CLASS: 'CHAR_CLASS',
-};
+});
 
 /**
 Replaces the given pattern only when it's unescaped and in the given context.