Merge pull request #30 from IKoshelev/patch-1

Update ch. 0, "Background information", JS sample

src/0_background_information.md

@@ -522,8 +522,8 @@ function timer(ms) {
 }
 
 timer(200)
-.then(() => return timer(100))
-.then(() => return timer(50))
+.then(() => timer(100))
+.then(() => timer(50))
 .then(() => console.log("I'm the last one"));
 ```