fix: return empty string if null or undefined value is passed

src/dates/format-date.js

@@ -176,6 +176,9 @@ formatters.Q = formatQuarter;
 
 export default function formatDate(date, format, locale = "en") {
     if (!isDate(date)) {
+        if (date === undefined || date === null) {
+            return '';
+        }
         return date;
     }
 

src/format.js

@@ -13,7 +13,7 @@ export function toString(value, format, locale) {
         }
     }
 
-    return value !== undefined ? value : "";
+    return value !== undefined && value !== null ? value : "";
 }
 
 export function format(format, values, locale) {

test/dates.js

@@ -29,6 +29,11 @@ describe('date formatting', () => {
         expect(formatDate("foo")).toEqual("foo");
     });
 
+    it('returns empty string if value is null or undefined', () => {
+        expect(formatDate(undefined)).toEqual("");
+        expect(formatDate(null)).toEqual("");
+    });
+
     it('applies short date format if no format is set', () => {
         expect(formatDate(date(2000, 1, 30))).toEqual("1/30/2000");
     });

test/format.js

@@ -35,6 +35,10 @@ describe('toString', () => {
         expect(toString(undefined, "c", "en")).toBe("");
     });
 
+    it('returns empty string if the value is null', () => {
+        expect(toString(null, "c", "en")).toBe("");
+    });
+
     it('returns the value if the format is not defined', () => {
         expect(toString(10)).toBe(10);
     });

test/numbers.js

@@ -47,8 +47,9 @@ describe('formatNumber', () => {
         expect(formatNumber()).toEqual("");
     });
 
-    it('should return empty string if null value is passed', () => {
+    it('should return empty string if null or undefined value is passed', () => {
         expect(formatNumber(null)).toEqual("");
+        expect(formatNumber(undefined)).toEqual("");
     });
 
     it('should return value if not finite value is passed', () => {