nullish coalescing operator

Author: roeib

README.md

@@ -374,3 +374,19 @@ window.addEventListener('contextmenu', ()=>{
 //With defer, browser will run your script when the page finished parsing. (not necessary finishing downloading all image files. 
 <script defer src="myscript.js"></script>
 ```
+
+#   nullish coalescing operator
+```javascript
+
+// an equality check against nullary values (e.g. null or undefined). Whenever the expression to the left of the ?? operator evaluates to either //undefined or null, the value defined to the right will be returned.
+
+const foo = undefined ?? 'default string';
+console.log(foo);
+// expected output: "default string"
+
+
+const age = 0 ?? 30;
+console.log(age);
+// expected output: "0"
+```
+