Clarify introductory clause.

Fix comma splice.

Author: XP1

doc/en/array/constructor.md

@@ -11,10 +11,10 @@ when creating new arrays.
     new Array(3); // Result: []
     new Array('3') // Result: ['3']
 
-In cases when there is only one argument passed to the `Array` constructor,
-and that argument is a `Number`, the constructor will return a new *sparse* 
+In cases when there is only one argument passed to the `Array` constructor
+and when that argument is a `Number`, the constructor will return a new *sparse* 
 array with the `length` property set to the value of the argument. It should be 
-noted that **only** the `length` property of the new array will be set this way, 
+noted that **only** the `length` property of the new array will be set this way; 
 the actual indexes of the array will not be initialized. 
 
     var arr = new Array(3);