Miscellaneous small fixes spotted by readers

Issue marijnh#260
Issue marijnh#258
Issue marijnh#256
Issue marijnh#254

Author: marijnh

04_data.md

@@ -1218,11 +1218,11 @@ like a good approach.
 
 {{index serialization, "World Wide Web"}}
 
-What we can do _serialize_ the data. That means it is converted into a
-flat description. A popular format is called _((JSON))_ (pronounced
-“Jason”), which stands for JavaScript Object Notation. It is widely
-used as a data storage and communication format on the Web, even in
-languages other than JavaScript.
+What we can do is _serialize_ the data. That means it is converted
+into a flat description. A popular format is called _((JSON))_
+(pronounced “Jason”), which stands for JavaScript Object Notation. It
+is widely used as a data storage and communication format on the Web,
+even in languages other than JavaScript.
 
 {{index array, object, [quoting, "in JSON"], comment}}
 

07_robot.md

@@ -73,7 +73,7 @@ function buildGraph(edges) {
 const roadGraph = buildGraph(roads);
 ```
 
-Given a an array of edges, `buildGraph` creates a map object that, for
+Given an array of edges, `buildGraph` creates a map object that, for
 each node, stores an array of connected nodes.
 
 {{index "split method"}}

20_node.md

@@ -607,7 +607,7 @@ and the request object that was returned from `http.request`.
 Writable streams are a widely used concept in Node. Such objects have
 a `write` method, which can be passed a string or a `Buffer` object,
 to write something to the stream. Their `end` method also optionally
-takes a value two write to the stream, and will close the steam after
+takes a value to write to the stream, and will close the steam after
 writing—or right away if none is given. Both of these methods can also
 be given a callback as an additional argument, which they will call
 when the writing to or closing of the stream has finished.

code/solutions/03_3_bean_counting.js

@@ -1,6 +1,6 @@
 function countChar(string, ch) {
-  var counted = 0;
-  for (var i = 0; i < string.length; i++) {
+  let counted = 0;
+  for (let i = 0; i < string.length; i++) {
     if (string[i] == ch) {
       counted += 1;
     }

code/solutions/04_3_a_list.js

@@ -15,7 +15,7 @@ function listToArray(list) {
 }
 
 function prepend(value, list) {
-  return {value, rest};
+  return {value, rest: list};
 }
 
 function nth(list, n) {