Errata

In the answer for Specimen #2, the following line should NOT have the parenthesis because it is supposed to be returning a function reference:

return getValue();

Two other code references earlier in the same chapter have this line code correct.

Note from the Author or Editor:
I'm not seeing the parentheses on the return statement for specimen #2 in the print book.

However the version in Safari books online is wrong. Please fix.

In the "How the Click me! closure works" section on Safari, under Extreme JavaScript Challenge Revisited, under Specimen #2, the line

return getValue();

should read

return getValue;

The image of HTML code is missing the ending </head> tag.

Note from the Author or Editor:
Fixed

I don't have a page number because I am using SafariOnlineBooks on my IPAD. In Chapter 9 there is an exercise that uses setInterval to display the value Tick or Tock. The output should say Tick then tock and so forth. The example in the book only shows the value Tick. At the end of the chapter where the answers are, the values are correct.

Note from the Author or Editor:
Please fix in Safari. It's fine in the printed book and PDF.

The annotation "And this whole thing is an expression" is too long - it includes the semicolon that terminates the statement. Instead, it should stop just before the semicolon.

Note from the Author or Editor:
Fixed!

The string provided to the prompt function is different from the string in the prompt dialog box that displays when prompt is called. The string in the code is missing the word ?from,? which appears in the dialog box between ?number? and ?0?6.? The same assignment statement also appears on p. 52, second to last line of code.

Note from the Author or Editor:
fixed

In the annotation that begins with ?But, with the boolean OR operator we can combine the tests so that if location matches any of location1, location2 or location3??, the word ?location? should read ?guess? (i.e., the variable).

Note from the Author or Editor:
fixed

There is a posting (from Mr. Yang) that is still under _unconfirmed_.

Where it is pointed out that the text says "passing values as parameters" when it SHOULD say arguments.

In fact the 5th from last paragraph says: Function: Oh, that's just another name for the values you pass into a function... they're the arguments of the function call."

But then the 4th.. Head First: Well you don't seem all that great... I mean, okay you allow me to reuse code, and you have this way of passing values as parameters. Is that it? ... "

Don't these two things contradict themselves? And kinda prove that this should be in the CONFIRMed errata?

Cheers

Note from the Author or Editor:
Change "Well you don’t seem all that great; I mean, okay you allow me to reuse code, and you have this way of passing values as parameters." to

"Well you don’t seem all that great; I mean, okay you allow me to reuse code, and you have this way of passing values into parameters."

4th block from the end, page 88

Parameters are local variables. So width, height, x1, y1, x2, y2 and r should be added to the Locals box.

Also in the setup function the parameters width and height shadow the global variables,
and should be circled.

Note from the Author or Editor:
fixed part 2; left part 1 (we are distinguishing between local variables and parameters in this exercise).

"Creates another new item in the next open index" Well since you've introduced sparse arrays I think "next open index" could be misunderstood here. My understanding is that it's always after the last array element.

Note from the Author or Editor:
I agree, the language is a bit ambiguous on this.

I've updated the annotations in the files for the next printing.

pg 164 and 171
function getMostCostEffectiveSolution(scores, costs, highscore)

and

if (scores[i] == highscore)

>>> highscore parameter is all in lowercase.

Note from the Author or Editor:
Fixed for next printing - changed all occurrences to highScore.

It should read "SCORES" instead of "SCORE".

Note from the Author or Editor:
fixed

The alternate solution in the bubbles2.html file has an error. The last line of the getMostCostEffectiveSolution2 function reads cost = costs[i];. It should read cost = costs[solutionIndex];.

Note from the Author or Editor:
Yes, fixed and code in github updated.

It should have been alert("Zoom zoom!"); instead of alert.log("Zoom zoom!");

Note from the Author or Editor:
yes. I've fixed for the next printing.

dog.bark listed as answer at bottom of page. Never assigned, bark was and should be answer as printed. Else assign woofs to dog.bark

Note from the Author or Editor:
Yup! It's fixed in the files for the next printing!

"This reference" and similar point to objects
"these objects'' more or less points to references
As I understand it, the references are represented by the things in the cups and the objects by the round blobs.

Note from the Author or Editor:
Fixed the arrows.

Boolean value false is missing from the list of falsey values, and the text talks of five, though it should say there are six. See also page 306.

Note from the Author or Editor:
Actually false isn't falsey. It's just false. I added an annotation to hopefully clarify a bit.

Possible misunderstanding:

Description of toUpperCase method says: "Returns a string with all lowercase characters changed to uppercase."

Original string does not have to be all lowercase but may contain characters of arbitrary case.

Fix: Change "all" to "every"

Note from the Author or Editor:
Fixed

The bullet point regarding the five falsey values states that false is falsy. It should read, NaN is falsey.

Note from the Author or Editor:
Already fixed

"06" should be "60"

Note from the Author or Editor:
fixed in chapter 8 file.

Missing var:

locations = ship.locations;

Note from the Author or Editor:
fixed

Not exactly error but firstChar seems to be used as a global through page 354. It's eliminated entirely in final code. Oh, and I'm not sure what a "non-null" string is. Is there such a thing as a "null string"?

Note from the Author or Editor:
It's used in the next line. However there is an error in that we don't declare the variable, so I've fixed that. I've also updated the code online to reflect using this variable (we'd eliminated it by combining that line with the next one).

you're right about "non-null string" there is no such thing as a null string, it should just say null. I've fixed that too. thanks.

To generate the integers 0-4 for the col shouldn't the multiplier be 5 instead of 4 (this.boardSize -2)? The same applies to page 367: this.boardSize - this.shipLength + 1.

Note from the Author or Editor:
Why yes, yes it should. Silly mistake. I've updated to change to 2 on page 366, and modify the annotation, and add 1 to shipLength on page 367.

The code in the book says we define the variable:

var ship = model.ships[i];

This works but since collision is a method within the "model" object shouldn't we reference the "ships" property in that object by using:

var ship = this.ships{i};

I've tested both ways which work. Is there any hazards to be aware of with one or the other?

Note from the Author or Editor:
In line 3 of the code on page 368 change "model" to "this". The code works either way, but "this" is more correct than "model".

Do NOT change the braces to {}; leave as is as [ ]

The solution says all six guesses are hits. The 1st, 3rd, and 5th ones are actually misses.

Note from the Author or Editor:
fixed

Annotation reads: "We create a function init. and assign it to the onload handler?".

IMHO onload is the event and init is the handler, no?

Fix: change "onload handler" to "onload event".

Note from the Author or Editor:
Changed to read "property" instead.

window.onload is now set to a anonymous function instead of to an init function as instructed on p. 389 and 390, but the notation next to the code states "This code is just as we wrote it before. No changes here..."

Note from the Author or Editor:
change "window.onload = function() {" to

window.onload = init;
function init() {

at the top of the code on page 412.

The Question asked about showAnswer defining reblur "in its code". As listed in text, it's separate. That works. I tried inserting reblur's definition inside showAnswer and that worked too.

Note from the Author or Editor:
modified the wording slightly.

Inconsistency between book and example code:

Book: function resize() { ? }
Example: function resize(e) { ? }

Parameter "e" is used nowhere in code.

Fix: remove "e" from example code.

Note from the Author or Editor:
fixed in code

Because of the "return false;" the function will print only the first name.

Note from the Author or Editor:
fixed

if (passenger.paid === true) {
should be replaced with
if (passenger.paid) {

This is exactly what was mentioned in the "Can we talk about your verbosity..." on page 65.

And there is no need for "return false;" at the end of the function, because at this point a reader knows that without that statement the function will return undefined, which is falsy.

Note from the Author or Editor:
left the return false, but removed the === true

this is a function declaration -- ending semi-colon not needed.

Note from the Author or Editor:
Remove semi-colon after the cookieAlarm function definition (after the closing }).

So it will read:

function cookieAlarm() {
alert("Time to take the cookies out of the oven");
}

Missing var on for loops.

I fixed it.

Seems like the annotation may have moved up the page, now points to </style> when the script section was intended.

Note from the Author or Editor:
Moved the annotation down a bit.

Duplicate closing tags in example file:

</script>
</head>
<body>
</body>
</html>

Note from the Author or Editor:
Update in code only (github)

The comment says: "…each dog has its own bark function…". Since we're talking objects here, should this not be "bark method" instead?

…just sayin'… ;)

Note from the Author or Editor:
EDITOR: Fixed a typo on this page and updated one annotation, both checked into svn.

You only have four, five are needed.

Note from the Author or Editor:
Good catch! I added two more ;-)

An extension of / follow-up to Dave Murley's posting of May 18, 2014: Semicolons are missing at the ends of several assignment statements. For example, from page 581,
Dog.prototype.sit = function() { console.log(this.name + " is now sitting"); }
Although the function expression doesn't need a semicolon, the assignment of the expression to Dog.prototype.sit does need one. On pages 583 and 617, this appears for Game.prototype.play and Game.prototype.unlock assignment statements.

Note from the Author or Editor:
Yes, fixed on 581, 583, 617.

Per page 13 in the regular text assignment statements are terminated with semicolons. None are used in the exercise, the solution or the download code.

The sample output is wrong as per the code Robby gets the laser first.

Note from the Author or Editor:
I fixed the output but need clarification on the other part of the errata. Not sure what you mean by "regular text assignments are terminated with semicolons".

I've checked the code and it looks to me like I'm using semicolons in all the right places...

Original: "…so all robots will inherit these methods."

From my understanding only robots based on the Space Robot prototype will inherit these but not Robbie and Rosie.

Suggested fix: "…so all space robots will inherit these methods."

Note from the Author or Editor:
I fixed page 619 to reflect this change.

If a string is a palindrome and has an even length,
the function will check all the characters twice.

For example, if we execute
"noon".palindrome();
the function will compare characters at position 0 and 3, 1 and 2, 2 and 1, 3 and 0.

We can fix that by changing the test in the for loop and by removing the 2nd if statement:

String.prototype.palindrome = function() {
var len = this.length - 1;
for (var i = 0; i < len/2; i++) {
if (this.charAt(i) !== this.charAt(len - i)) {
return false;
}
}
return true;
};

This code works correctly and does the minimal number of comparisons in all cases.

Note from the Author or Editor:
Yes! Slightly more efficient code. Except I think you need the <= on the for loop.

EDITOR: I've updated page 621 in SVN to reflect this change.

http://techbus.safaribooksonline.com/book/programming/javascript/9781449340124/7dot-types-equality-conversion-and-all-that-jazz-serious-types/chair_wars_left_parenthesisor_how_really_html

Under the section Bullet Points, the following fails to mention NaN as one of the five type mentioned earlier in the chapter:

JavaScript has five falsey values: undefined, null, 0, ?? (the empty string) and false. All other values are truthy.

Note from the Author or Editor:
Yup! Fixed in the files for next printing.