Pass over chapter 4

Lots of cleanup, try to make correlation formula less intimidating,
add rest params, destructuring.

Author: marijnh

03_functions.md

@@ -484,11 +484,11 @@ console.log(power(2, 6));
 
 {{index "console.log"}}
 
-In the [next chapter](04_data.html#arguments_object), we will see a
-way in which a function body can get at the exact list of arguments
-that were passed. This is helpful because it makes it possible for a
-function to accept any number of arguments. For example, `console.log`
-makes use of this—it outputs all of the values it is given.
+In the [next chapter](04_data.html#rest_parameters), we will see a way
+in which a function body can get at the whole list of arguments it was
+passed. This is helpful because it makes it possible for a function to
+accept any number of arguments. For example, `console.log` makes use
+of this—it outputs all of the values it is given.
 
 ```
 console.log("C", "O", 2);
@@ -1055,11 +1055,10 @@ hint}}
 
 ### Bean counting
 
-{{index "bean counting (exercise)", "charAt method", [string, indexing], "zero-based counting"}}
+{{index "bean counting (exercise)", [string, indexing], "zero-based counting"}}
 
 You can get the Nth character, or letter, from a string by writing
-`"string".charAt(N)`, similar to how you get its length with
-`"s".length`. The returned value will be a string containing only one
+`"string"[N]`. The returned value will be a string containing only one
 character (for example, `"b"`). The first character has position zero,
 which causes the last one to be found at position `string.length - 1`.
 In other words, a two-character string has length 2, and its

04_data.md

@@ -211,7 +211,7 @@ HTML documents have a head and a body.
 The head contains information _about_ the document, and the body
 contains the document itself. In this case, we first declared that the
 title of this document is “My home page” and then gave a document
-containing a heading (`<h1>`, meaning “heading 1”—_<h2>_ to `<h6>`
+containing a heading (`<h1>`, meaning “heading 1”—_`<h2>`_ to `<h6>`
 produce more minor headings) and two ((paragraph))s (`<p>`).
 
 {{index "href attribute", "a (HTML tag)"}}

12_browser.md

@@ -1,4 +1,4 @@
-var JOURNAL = [
+const JOURNAL = [
   {"events":["carrot","exercise","weekend"],"squirrel":false},
   {"events":["bread","pudding","brushed teeth","weekend","touched tree"],"squirrel":false},
   {"events":["carrot","nachos","brushed teeth","cycling","weekend"],"squirrel":false},
@@ -92,6 +92,6 @@ var JOURNAL = [
 ];
 
 // This makes sure the data is exported in node.js —
-// `require('./path/to/04_data.js')` will get you the array.
+// `require('./path/to/jaques_journal.js')` will get you the array.
 if (typeof module != "undefined" && module.exports)
   module.exports = JOURNAL;

code/jacques_journal.js

@@ -1,7 +1,7 @@
 function countChar(string, ch) {
   var counted = 0;
   for (var i = 0; i < string.length; i++) {
-    if (string.charAt(i) == ch) {
+    if (string[i] == ch) {
       counted += 1;
     }
   }

code/solutions/03_3_bean_counting.js

@@ -1,21 +1,19 @@
-function range(start, end, step) {
-  if (step == null) step = 1;
-  var array = [];
+function range(start, end, step = start < end ? 1 : -1) {
+  let array = [];
 
   if (step > 0) {
-    for (var i = start; i <= end; i += step)
-      array.push(i);
+    for (let i = start; i <= end; i += step) array.push(i);
   } else {
-    for (var i = start; i >= end; i += step)
-      array.push(i);
+    for (let i = start; i >= end; i += step) array.push(i);
   }
   return array;
 }
 
 function sum(array) {
-  var total = 0;
-  for (var i = 0; i < array.length; i++)
+  let total = 0;
+  for (let i = 0; i < array.length; i++) {
     total += array[i];
+  }
   return total;
 }
 

code/solutions/04_1_the_sum_of_a_range.js

@@ -1,13 +1,14 @@
 function reverseArray(array) {
-  var output = [];
-  for (var i = array.length - 1; i >= 0; i--)
+  let output = [];
+  for (let i = array.length - 1; i >= 0; i--) {
     output.push(array[i]);
+  }
   return output;
 }
 
 function reverseArrayInPlace(array) {
-  for (var i = 0; i < Math.floor(array.length / 2); i++) {
-    var old = array[i];
+  for (let i = 0; i < Math.floor(array.length / 2); i++) {
+    let old = array[i];
     array[i] = array[array.length - 1 - i];
     array[array.length - 1 - i] = old;
   }
@@ -16,7 +17,7 @@ function reverseArrayInPlace(array) {
 
 console.log(reverseArray(["A", "B", "C"]));
 // → ["C", "B", "A"];
-var arrayValue = [1, 2, 3, 4, 5];
+let arrayValue = [1, 2, 3, 4, 5];
 reverseArrayInPlace(arrayValue);
 console.log(arrayValue);
 // → [5, 4, 3, 2, 1]

code/solutions/04_2_reversing_an_array.js

@@ -1,28 +1,27 @@
 function arrayToList(array) {
-  var list = null;
-  for (var i = array.length - 1; i >= 0; i--)
+  let list = null;
+  for (let i = array.length - 1; i >= 0; i--) {
     list = {value: array[i], rest: list};
+  }
   return list;
 }
 
 function listToArray(list) {
-  var array = [];
-  for (var node = list; node; node = node.rest)
+  let array = [];
+  for (let node = list; node; node = node.rest) {
     array.push(node.value);
+  }
   return array;
 }
 
 function prepend(value, list) {
-  return {value: value, rest: list};
+  return {value, rest};
 }
 
 function nth(list, n) {
-  if (!list)
-    return undefined;
-  else if (n == 0)
-    return list.value;
-  else
-    return nth(list.rest, n - 1);
+  if (!list) return undefined;
+  else if (n == 0) return list.value;
+  else return nth(list.rest, n - 1);
 }
 
 console.log(arrayToList([10, 20]));

code/solutions/04_3_a_list.js

@@ -2,24 +2,25 @@ function deepEqual(a, b) {
   if (a === b) return true;
 
   if (a == null || typeof a != "object" ||
-      b == null || typeof b != "object")
-    return false;
+      b == null || typeof b != "object") return false;
 
-  var propsInA = 0, propsInB = 0;
+  let propsInA = 0, propsInB = 0;
 
-  for (var prop in a)
+  for (let prop in a) {
     propsInA += 1;
+  }
 
-  for (var prop in b) {
+  for (let prop in b) {
     propsInB += 1;
-    if (!(prop in a) || !deepEqual(a[prop], b[prop]))
+    if (!(prop in a) || !deepEqual(a[prop], b[prop])) {
       return false;
+    }
   }
 
   return propsInA == propsInB;
 }
 
-var obj = {here: {is: "an"}, object: 2};
+let obj = {here: {is: "an"}, object: 2};
 console.log(deepEqual(obj, obj));
 // → true
 console.log(deepEqual(obj, {here: 1, object: 2}));

code/solutions/04_4_deep_comparison.js

@@ -15,6 +15,7 @@ let baseCode = "let alert = function() {}, prompt = function() { return 'x' }, c
 let meta = /\{\{meta (.*?)\}\}\n/.exec(input)
 let include = /\bload_files: (\[[^\]]+\])/.exec(meta ? meta[1] : "")
 if (include) JSON.parse(include[1]).forEach(function(fileName) {
+  if (fileName == "code/chapter/" + file.replace(/md/, "js")) return
   let text = fs.readFileSync("html/" + fileName)
   if (!/\/\/ test: no/.test(text))
     baseCode += text