test: add check for inherited Object property names in StrEnum

Author: mceachen

src/StrEnum.spec.ts

@@ -37,6 +37,15 @@ describe("StrEnum", () => {
       expect(Examples.indexOf(v)).to.eql(idx);
     });
   }
+
+  it("does not accept inherited Object property names", () => {
+    for (const v of ["constructor", "toString", "__proto__", "valueOf"]) {
+      expect(Examples.has(v)).to.eql(false);
+      expect(Examples.includes(v)).to.eql(false);
+      expect(Examples.indexOf(v)).to.eql(undefined);
+    }
+  });
+
   for (const { v, exp } of fixtures) {
     it(`.toValid(${v}) -> ${exp ? v : "undefined"}`, () => {
       expect(Examples.toValid(v)).to.eql(exp ? v : undefined);

src/StrEnum.ts

@@ -204,7 +204,7 @@ export function strEnum<T extends string>(...o: T[]): StrEnum<T> {
   const lcToValue = new Map<string, T>(
     values.map((ea) => [ea.toLowerCase(), ea]),
   );
-  const valueToIndex = Object.fromEntries(
+  const valueToIndex = new Map<string, number>(
     values.map((ea, idx) => [ea as string, idx]),
   );
 
@@ -218,7 +218,7 @@ export function strEnum<T extends string>(...o: T[]): StrEnum<T> {
     s == null ? undefined : lcToValue.get(s?.toLowerCase());
 
   const indexOf = (s: Nullable<string>) =>
-    s != null ? valueToIndex[s] : undefined;
+    s != null ? valueToIndex.get(s) : undefined;
 
   const ordinal = (s: Nullable<string>) => indexOf(s) ?? values.length;