[Sabrina] Fix typos in code snippets

Author: sabrina-tw

docs/javascript/classes.md

@@ -173,10 +173,10 @@ c.area; // data is exposed as a property
 We also can use a setter.
 
 ```js
-class Person = {
+class Person {
   constructor(firstName, lastName) {
     this.firstName = "John";
-    this.lastName: "Doe";
+    this.lastName = "Doe";
     this.language = "";
   }
 

docs/javascript/loops.md

@@ -49,7 +49,7 @@ for (variable of iterable) {
 ```js
 const numbers = [10, 20, 30];
 for (const number of numbers) {
-  console.log(value);
+  console.log(number);
 }
 ```