Use comma for introductory clauses.

Clarify introductory clause by repeating the first word.
Use "which" instead of "that".

Author: XP1

doc/en/array/general.md

@@ -1,15 +1,15 @@
 ## Array Iteration and Properties
 
 Although arrays in JavaScript are objects, there are no good reasons to use
-the [`for in loop`](#object.forinloop) in for iteration on them. In fact there 
+the [`for in loop`](#object.forinloop) in for iteration on them. In fact, there 
 are a number of good reasons **against** the use of `for in` on arrays.
 
 > **Note:** JavaScript arrays are **not** *associative arrays*. JavaScript only 
 > has [objects](#object.general) for mapping keys to values. And while associative 
 > arrays **preserve** order, objects **do not**.
 
-Since the `for in` loop enumerates all the properties that are on the prototype 
-chain and the only way to exclude those properties is to use 
+Because the `for in` loop enumerates all the properties that are on the prototype 
+chain and because the only way to exclude those properties is to use 
 [`hasOwnProperty`](#object.hasownproperty), it is already up to **twenty times** 
 slower than a normal `for` loop.
 
@@ -23,7 +23,7 @@ to use the classic `for` loop.
         console.log(list[i]);
     }
 
-There is one extra catch in the above example, that is the caching of the 
+There is one extra catch in the above example, which is the caching of the 
 length of the array via `l = list.length`.
 
 Although the `length` property is defined on the array itself, there is still an
@@ -52,7 +52,7 @@ does not have any effect on the array.
 
 ### In Conclusion
 
-For the best performance it is recommended to always use the plain `for` loop
+For the best performance, it is recommended to always use the plain `for` loop
 and cache the `length` property. The use of `for in` on an array is a sign of
 badly written code that is prone to bugs and bad performance.