Misc typo fixes

Closes #266
Closes #264
Closes #267

Author: marijnh

02_program_structure.md

@@ -95,7 +95,7 @@ let caught = 5 * 5;
 
 {{index "let keyword"}}
 
-That's a a second kind of ((statement)). The special word
+That's a second kind of ((statement)). The special word
 (_((keyword))_) `let` indicates that this sentence is going to define
 a binding. It is followed by the name of the binding and, if we want
 to immediately give it a value, by an `=` operator and an expression.

03_functions.md

@@ -599,9 +599,9 @@ console.log(power(2, 3));
 {{index loop, readability, mathematics}}
 
 This is rather close to the way mathematicians define exponentiation
-and arguably describes the concept in a more clearly way than the
-looping variant does. The function calls itself multiple times with
-ever smaller exponents to achieve the repeated multiplication.
+and arguably describes the concept more clearly than the looping
+variant does. The function calls itself multiple times with ever
+smaller exponents to achieve the repeated multiplication.
 
 {{index [function, application], efficiency}}
 

06_object.md

@@ -334,8 +334,9 @@ through it but is not its _own_ prototype.
 ## Class notation
 
 So JavaScript ((class))es are ((constructor)) functions with a
-((prototype)) property. That how they work, and until 2015, that's how
-you had to write them. These days, we have a less awkward notation.
+((prototype)) property. That is how they work, and until 2015, that
+was how you had to write them. These days, we have a less awkward
+notation.
 
 ```{includeCode: true}
 class Rabbit {

10_modules.md

@@ -60,7 +60,7 @@ to use (its _((interface))_).
 {{index "big ball of mud"}}
 
 Module interfaces have a lot in common with object interfaces, as we
-saw them in [Chapter ?](objects#interface). They make part of the
+saw them in [Chapter ?](object#interface). They make part of the
 module available to the outside world, and keep the rest private. By
 restricting the ways in which modules interact with each other, the
 system becomes more like ((Lego)), where pieces interact through