🕷️ Fix NaN issue in signum

SpiderMath · SpiderMath · commit 486c5e88ff3b · 2022-11-28T09:12:47.000+05:30
diff --git a/Maths/Signum.js b/Maths/Signum.js
@@ -12,10 +12,11 @@
 
 /**
  * @param {Number} input
- * @returns {-1 | 0 | 1} sign of input
+ * @returns {-1 | 0 | 1 | NaN} sign of input (and NaN if the input is NaN)
  */
 function signum (input) {
-  if (input === 0) return 0
+  if(isNaN(input)) return NaN
+  else if (input === 0) return 0
   else if (input < 0) return -1
   else return 1
 }
diff --git a/Maths/test/Signum.test.js b/Maths/test/Signum.test.js
@@ -12,4 +12,8 @@ describe('The sign of a number', () => {
   it('Sign of -420', () => {
     expect(signum(-420)).toBe(-1)
   })
+
+  it('Sign of NaN', () => {
+    expect(signum(NaN)).toBe(NaN)
+  })
 })
