Update 01_javascript_refresher.md

Some errors in text

01_Day_JavaScript_Refresher/01_javascript_refresher.md

@@ -3843,7 +3843,7 @@ class Person {
 }
 ```
 
-We have created an Person class but it does not have any thing inside.
+We have created a Person class but it does not have any thing inside.
 
 #### Class Instantiation
 
@@ -3869,7 +3869,7 @@ Let use the class constructor to pass different properties for the class.
 
 #### Class Constructor
 
-The constructor is a builtin function which allows as to create a blueprint for our object. The constructor function starts with a keyword constructor followed by a parenthesis. Inside the parenthesis we pass the properties of the object as parameter. We use the _this_ keyword to attach the constructor parameters with the class.
+The constructor is a builtin function which allows us to create a blueprint for our object. The constructor function starts with a keyword constructor followed by a parenthesis. Inside the parenthesis we pass the properties of the object as parameter. We use the _this_ keyword to attach the constructor parameters with the class.
 
 The following Person class constructor has firstName and lastName property. These properties are attached to the Person class using _this_ keyword. _This_ refers to the class itself.