src/algorithms/math/fast-powering/__test__/fastPowering.test.js

@@ -19,5 +19,8 @@ describe('fastPowering', () => {
     expect(fastPowering(16, 16)).toBe(18446744073709552000);
     expect(fastPowering(7, 21)).toBe(558545864083284000);
     expect(fastPowering(100, 9)).toBe(1000000000000000000);
+    expect(fastPowering(5, -5)).toBe(0.0003200000000000002);
+    expect(fastPowering(-5, 5)).toBe(-3125);
+    expect(fastPowering(-5, -5)).toBe(-0.0003200000000000002);
   });
 });

src/algorithms/math/fast-powering/fastPowering.js

@@ -14,6 +14,12 @@ export default function fastPowering(base, power) {
     return 1;
   }
 
+  if (power < 0) {
+    const powerNext = power * -1;
+    const baseNext = 1 / base;
+    return fastPowering(baseNext, powerNext);
+  }
+
   if (power % 2 === 0) {
     // If the power is even...
     // we may recursively redefine the result via twice smaller powers: