Errata

Meta-erratum: On the errata page, "rather that" should be "rather than" in this correction:

"Functions defined as expressions (rather that with a declaration) are not hoisted…"

After "Constant width bold", the following line has no period at the end, unlike the similar explanatory lines that precede it on the same and previous page:

"Shows commands or other text that should be typed literally by the user"

Suggested fix: Add period.

Error in the errata
The errata for page 37 mentions that section 3.2.3 is on page 37 but it's on page 27.

Note from the Author or Editor:
(how meta!)

In the 4th line, the final "y" in the word "they" is missing. The line begins with:

default, the are in base 10, but you can use the .....

And it should say:

default, they are in base 10, ...

The line says:

JavaScript programs word with numbers using the arithmetic operators . that the language provides.

The "." between "operators" and "that" should be removed.

Note from the Author or Editor:
Please remove the stray period in the first line of section 3.2.3 "Arithmetic in JavaScript"

The line reads:
... and iterable objects (chapter 12), it needed to define standard method that classes ....


The article 'a' is missing before 'standard'.

Note from the Author or Editor:
Please change "it needed to define standard method" to read "it needed to define a standard method"

Maybe "constructor" should be "constructors" (plural) in this sentence:

"As an aside, note that the Boolean(), Number(), and String() functions can also be invoked—with new—as constructor.

Note from the Author or Editor:
Change "as constructor" to "as constructors"

The code example displays a different output than what I experience when running this example under Chrome.

Original code follows:
let d = new Date(2010, 0, 1);
d.valueOf();

The book suggests the output of valueOf should be: 1262332800000
The output I obtained was: 1262264400000

I am unsure if this is due to a localisation issue of some type?

Note from the Author or Editor:
This is a timezone issue. The Date() constructor creates a date in local time, and you and I are in different timezones. Sorry for the confusion.

Please change:

// => 1262332800000

To:

// => 1262332800000; (timezone-dependent)

"It will be a global now deeply nested..." --> "It will be a global how deeply nested..."

now --> how

Note from the Author or Editor:
In the "Using Undeclared Variables" sidebar please change "no matter now deeply" to "no matter how deeply"

The word "and" seems superfluous in this sentence:

7 >> 1 evaluates to 3, for example, but note that and -7 >> 1 evaluates to -4.

Note from the Author or Editor:
Change "but not that and" to "but note that"

"propogates" should be "propagates"

The text has the word "comma" in monospace code font here:

"The comma operator is a binary operator..."

I wonder if the word "comma" should instead be set in normal text font, or maybe replaced with a literal comma character (",") in code font, for consistency with the descriptions of the other operators and to avoid implying that the word "comma" itself is a reserved word.

Note from the Author or Editor:
Set "comma" in roman not code font.

Where read:

"... The throw statement is a kind of interim return from a generator function. "

should be read:

"... The yield statement is a kind of interim return from a generator function. "

Note from the Author or Editor:
Thanks for pointing out this particularly dumb typo. You are correct that the sentence should read "The yield statement is a kind of interim return from a generator function". The very next sentence also begins "The throw statement" and that one is correct as it stands.

"If the block...does not have an associated catch clause, the interpreter checks the next-highest enclosing block..."

I feel like "next-highest" should be "next higher", since the directional metaphor in this paragraph is of exceptions propagating upward to higher levels. "Next-highest" seems to indicate stepping downward from the highest level.

Note from the Author or Editor:
Please delete "next-highest". The sentence is clear without it.

The first sentence refers to an octal literal with a '0' not followed by an 'x' but this in fact describes a hexadecimal literal. Instead, it should read:

"beginning with a 0 that is not followed by an o".

Note from the Author or Editor:
Thanks for pointing this out. That text dates to the days before JavaScript explicitly supported the '0o' notation.

Please change the parenthetical text "(beginning with a 0 that is not followed by an x)" to "(integers beginning with a 0 that is not followed by a b, o, or x)"

Maybe add "a", changing:
(such as function or class)
to:
(such as a function or class)

Note from the Author or Editor:
change "such as function" to "such as a function"

Maybe remove "and" from this sentence:

"Since p does not already exist in o, and if there is no setter method to call, then p must be added to o."

Note from the Author or Editor:
Change "and if there is no setter method" to "and since there is no setter method"

"For sparse arrays, length is larger than the highest index of any element."

This sentence seems to imply a difference with nonsparse arrays, however it is true of both.

Note from the Author or Editor:
Please change the final sentence of that paragraph so that it reads:

For sparse arrays, length is larger than the highest index of any element (but it does not tell us anything about the number of elements).

In the third line of second paragraph, instead of showing "true" in monospaced font, appears <code>true></code>. That line says:

<code>true></code> and only interates through the entire array if your predicate always

instead of

true and only interates through the entire array if your predicate always

Note from the Author or Editor:
Please change <code>true</code> to "true" in code font.

Looks like maybe the manual process of fixing bad line breaks went awry here?

In the second line of the first block of code, after the first paragraph, there is a line o f code that says:

a.some(x => x%2===0)

To use a good formatting style and to have a homogeneus style with a similar example (with the same predicate function) in the previos page, it should appear with a space before and after operators "%" and "===":

a.some(x => x % 2 === 0)

Note from the Author or Editor:
Please add the spaces that the reporter describes.
And then on the next line, add some spaces before the comment so that the comments are aligned.

"Note also that, by mathematical convention, every() returns true and some returns false when invoked on an empty array."

Maybe add parentheses, changing "some" to "some()" in this sentence, for consistency with the other mentions of every() and some() in this section.

Note from the Author or Editor:
Change "some" to "some()" and ensure that it remains in code font.

Original: "The length property is automatically updated as new elements are added to the list"

Question: 'list' or 'array'?

Note from the Author or Editor:
Please change the first bullet of section 7.9 "Array-like Objects" to end the sentence after "added", deleting "to the list."

"expression that defines" should be "expressions that define" in this sentence:

"This is not true for functions defined as expressions, however: these functions do not exist until the expression that defines them are actually evaluated."

Original: "Rest parameters and the spread operator are often useful together, as in the following function, which takes a function argument and returns an instrumented version of the function for testing:"

Issue: This is the only time the term "instrumented" is used in the book. Term has not been introduced.

Quesion: Does it make sense to give a short description of the concept of instrumentation?

Note from the Author or Editor:
That is a good point. The concept of instrumentation is illustrated by the code, so let's not define it here. Instead just replace "instrumented" with "wrapped", which is the term I used in the code comments, anyway.

Add "of", changing:

// Return the sum of the elements an iterable object a.

to:

// Return the sum of the elements of an iterable object a.

Appears "namesapce" instead of "namespace"

Original: "Here, for example, is a way to define the preceding not() function just shown using composition and partial application:" and

"We can also use composition and partial application to redo our mean and standard deviation calculations in extreme functional style:"

Issue: The term "composition" has not yet been introduced.

Suggestion: Add a short definition for the term "composition" as used in the book might be helpful although it is not absolutely necessary for the intended audience.

Note from the Author or Editor:
Change the sentence:

Here, for example, is a way to define the preceding not() function just shown using composition and partial application:

to:

Here, for example, is a way to define the not() function from the previous section using composition (i.e. the compose() function from the previous section) and partial application:

"Euclidian" => "Euclidean"

Original: Finally, also note the things that do not change between Examples 9-1 and 9-2 : the range methods are defined and invoked in the same way for both classes.

Issue: missing formatting and parentheses for "range".

Suggested fix: Format "range" as [cursive]range()[/cursive].

Note from the Author or Editor:
The word "range" is incorrect in this sentence but the suggested fix is incorrect.

Please change "the range methods are defined and invoked in the same way for both classes" to "the methods of both classes are defined and invoked in the same way"

Maybe add "the" or "a" between "name of" and "class"

Note from the Author or Editor:
Change "the name of class" to "the name of the class"

Original: // TypeError: r.parse is not a function

Issue: Missing ! before "TypeError"

Note from the Author or Editor:
Please change the code comment from:

// TypeError: r.parse is not a function

to:

// !TypeError: r.parse is not a function

(this notation is explained in the box on page 7)

"added to set" => "added to the set"

Original: "Range set is a concrete subclass of AbstractSet."

Issue: Subblass is actually called RangeSet

Suggested fix: Change "Range set" to "RangeSet".

Original: "If the other set is not also Enumerable, it isn't equal to this one"

Issue: Code tests for AbstractEnumerableSet: if (!(set instanceof AbstractEnumerableSet)), but comment says 'Enumerable'.

Suggested fix: Change comment to: ""If the other set is not also an AbstractEnumerableSet, it isn't equal to this one""

Note from the Author or Editor:
This comment is misleading as it stands. But using the full AbstractEnumerableSet classname would make it wrap on to a second line. So let's fix it by writing "enumerable" instead of "Enumerable" so that it is clear we're just using an adjective and not refering to a particular class name.

maybe "hood, constructor" => "hood, the constructor"

There is no space between module.exports and object. It reads:

"...or by replacing the module.exportsobject entirely."

whereas it should read instead:

"...or by replacing the module.exports object entirely."

Note from the Author or Editor:
Please insert the space. (This was a production error caused while fixing a bad line break)

"namspace" => "namespace"

The last sentence of the last paragraph of section 10.3.1 which is in parentheses has a slight grammatical error. The issue is with this part:

"a modules export will be the same on every run..."

Suggested change is:

"a module's export will be the same on every run"

I've added an apostrophe to "module's export" which indicates ownership.

Note from the Author or Editor:
In addition to adding the apostrophe, let's also make "exports" plural. Please change "a modules export" to "a module's exports"

Original: "A module specifier string must be an absolute path starting with “/”, or a relative path starting with “./” or “../”, or a complete URL a with protocol and hostname."

Issue: "…a complete URL a with protoco…". Unneccessary 'a' after 'URL'

Suggested fix: Remove 'a' and save it in case someone needs better grades. ;)

Note from the Author or Editor:
Please change "complete URL a with" to "complete URL with"

Original: "The exporting module can export any number of named value."

Suggested fix: Add plural 's': "The exporting module can export any number of named values."

Original: "…you can still import the module . just for that default behavior."

Issue: Period in the middle of a sentence.

Suggested fix: "…you can still import the module just for that default behavior."

Note from the Author or Editor:
Please remove the spurious period. (Git logs show it was accidentally inserted as part of the index creation process)

The third code line on the first code block incorrectly spells "stddev". This needs to be changed from "export { mean, stdev };" to "export { mean, stddev };"

Note from the Author or Editor:
Please change "export { mean, stdev };" to "export { mean, stddev };"

"transfered" => "transferred" (to match preceding sentence)

"used chained" => "use chained"

hyphenate "two element" => "two-element"

Note from the Author or Editor:
Change "two element" to "two-element"

Also, in the third code comment below this paragraph please change "// Same as new map(" to "// Same as new Map("

"DataView also defines 10 corresponding Set methods..."

Maybe "Set" should be lowercase and in code font to match "get" in the preceding paragraph.

Note from the Author or Editor:
Change "Set" to "set" and put it in code font.

"grammar: it is" => "grammar: each is"

Note from the Author or Editor:
Change "it is the name of a category of characters defined" to "they are names of character categories defined"

Original: In the preceding example, we were able to use a regular expression “backreference” to write a RegExp that would match a single- or double- quoted string where the open and close quotes had to match.

Issue: Example with quotes is previous page 288,

Suggested fix: "On the previous page, we were…" or simply "Earlier, we were…"

Note from the Author or Editor:
Please replace "In the preceding example" with "Earlier"

"matching the any named" => "matching any named"

Original: If you want to specify a date and time in UTC (Universal Coordinated Time, aka GMT), then you can use the Date.UTC().

Issue: Missing word at end of sentence.

Suggested fix: …then you can use the Date.UTC() method.

Sauce: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/UTC

Note from the Author or Editor:
Please remove the word "the", so that "you can use the Date.UTC()" becomes "you can use Date.UTC()"

"must to convert" => "must convert", and "characters than can" => "characters that can"

Maybe the property name 'style' should be in code font in both occurrences of:

'If style is "currency",'

Note from the Author or Editor:
Set the word "style" in code font in the two locations indicated.

"as format" => "as a format"

It says

".. to iterate though a “partially used” iterator"

but it was probably intended to say

".. to iterate through a “partially used” iterator"

That is "though" => "through"

Note from the Author or Editor:
Change though to through on the last line of prose on page 328

Appears

]

instead of

]

The exact text is

bol.Iterator]()

Note from the Author or Editor:
Please replace the HTML entitty &rbrack; with a plain right bracket in code font: ']'
(This error does not appear in the QC2 draft, so it must have crept in during one of the very final production steps.)

"method show in" => "method shown in"

Note from the Author or Editor:
Please change "show" to "shown" on the second to last line.

On the last line of the page, change "&rbrack;" to "]"

"if the we get" => "if we get"

Last phrase of the first paragraph says:

A .catch() callback can throw a new error, but if it returns normally, **than** that return value is used to resolve and/or fulfill the associated Promise, and the error stops propagating.

Change to be made:

than => then

Note from the Author or Editor:
Please change "than" to "then"

It says:

"...are designed the way **the** are."

Change to be made:

the => they

resulting in

"...are designed the way **they** are."

There's an extra unbalanced parenthesis in middle of the parenthetical sentence:

"in §14.3); see also the"

should be:

"in §14.3; see also the"

Original: Typed array classes use the Symbol in the same way that the Array class does.

Issue: not classy enough

Suggested fix: Add "class" after "Symbol".

Note from the Author or Editor:
The text is correct, but confusing as it is. I'm talking about this particular symbol under discussion Symbol.species. But because of the capitalization convention, it is not clear that I mean one particular symbol instead of the Symbol type. Adding "class" does not help. Let's fix this by naming the symbol explicitly.

Please change:

Typed array classes use the Symbol in the same way that the Array class does.

To:

Typed array classes use Symbol.species in the same way that the Array class does.

And set "Symbol.species" in code font as it is everywhere else in this section.

Suggestion: Remove the word "if" from this phrase:

"we'll find that if we can query the proxy...and it will tell us that we should be able..."

Alternatively, the word "if" could remain, and the words "can" and "and" could both be removed instead.

Note from the Author or Editor:
Change "that if we can query" to "that we can query"

The word "on" seems superfluous in:

"...work with XML documents on..."

Note from the Author or Editor:
Change "XML documents on" to "XML documents"

The first sentence of the 3rd paragraph seems to have a typo. Remove the "a" after the "the" so it says: "A <script" tag with the src attribute"

Note from the Author or Editor:
Please change "with the a src attribute" to "with a src attribute", deleting the extraneous "the"

Add "on", changing:

"whether it is a click a hyperlink."

to:

"whether it is a click on a hyperlink."

Note from the Author or Editor:
Change "click a hyperlink" to "click on a hyperlink"

"correspond" should be "corresponds" in:

"The DOM defines a style property...that correspond to the style attribute."

Note from the Author or Editor:
Change "correspond" to "corresponds". It is the singular style property that corresponds, not the Element objects.

Second sentence of the fifth paragraph.

Change the word "animate" to "animation" so it says "...triggers an animation".

Note from the Author or Editor:
Please change "triggers an animate" to "triggers an animation"

"listen form" => "listen for"

It seems like "it" should be "they" in:

"...the CSS overflow property allows elements...to contain more content than it can display."

Note from the Author or Editor:
Change "than it can display" to "than they can display"

"to to" => "to"

"that it is used" => "that is used"

I think "do" should be "don't" here:

// in the template and do have to parse the HTML again.

Note from the Author or Editor:
Please change "and do have to parse" to "and do not have to parse"

Maybe the 1st "size" is superfluous in:

"Instead, set the desired on-screen size CSS pixel size..."

Note from the Author or Editor:
Please change "on-screen size CSS pixel size" to "on-screen CSS pixel size"

maybe "try get" => "try to get"

Note from the Author or Editor:
Change "we try get" to "we try to get"

"is it" => "it is" in:

"With POST requests, is it..."

I think this paragraph (about the value "default") should be indented to match the indentation level of the next 4 paragraphs ("no-store", "reload", "no-cache", and "force-cache").

On the 5th paragraph before the code for the getCookies() function, the function is named in its non-plural form "getCookie()".

Note from the Author or Editor:
Please change "defines a getCookie() function" to "defines a getCookies() function"

"A" => "An"

"global postMesage()" => "global postMessage()"

"recieved" => "received"

"changes" => "change" ("parts...change")

"which we do" => "which we are"

(alternatively: no change to this line, and instead "we're" => "we get" in the preceding line)

Note from the Author or Editor:
Change this comment in the code:

// a second argument of false which we do when we get a popstate event

To:

// a second argument of false (when handling a popstate event, for example)

"logarithic" => "logarithmic"

"knowledge is is much" => "knowledge is much"

"visiblitychange" => "visibilitychange"

"themselves" => "itself"

unbalanced quotation marks in:

(using an <input type="file> form element)

Note from the Author or Editor:
Change:

<input type="file>

To:

<input type="file">

"enables" => "enable" ("allow...and enable")

Actual text is "Node makes these available though the process.env object"

It should be "through" instead of "though"

The next phrase contais a comma that mush be removed. In the form that appears in the printed version, the meaning of the phrase is just the opposite to the intended one:

... If you don no want unhandled rejections, to print error messages or terminate your program, register a global handler function:

....

==> remove the comma after "rejections"

Note from the Author or Editor:
The sentence should read:

If you do not want unhandled rejections to print error messages or terminate your program, register a global handler function:

"they becomes" => "they become"

The comment for os.networkInterfaces() has a period after the word "network".

Note from the Author or Editor:
Please change "network. connections" to "network connections"

"they bytes" => "the bytes" or "they"

Note from the Author or Editor:
Change "that they bytes" to "that the bytes"

Appears:

Two flags are combined with the bitwise OR opeartor | . The flags mean that

Change to be done: opeartor => operator

Note from the Author or Editor:
Please change "opeartor" to "operator"

There is a missing comma between "string" and "then" in the first line of comments:

Convert the body object to a JSON string then HTTPS POST ...

should appear:

Convert the body object to a JSON string, then HTTPS POST ...

or

Convert the body object to a JSON string and then HTTPS POST ...

The original code block is:

/*
* Convert the body object to a JSON string then HTTPS POST it to the
* specified API endpoint on the specified host. When the response arrives,
* parse the response body as JSON and resolve the returned Promise with
* that parsed value.
*/

I suppose the best option is the first one, to maintain uniformity with a phrase that has the same structure and that appears 6 lines below:

// Return a Promise object immediately, then call resolve or reject

Note from the Author or Editor:
Honestly, my grasp of grammar rules for commas is shaky enough that I don' t know if it is actually an error to omit that comma. But I agree that it is clearer with a comma.

The first occurrence of "type" seems superfluous in:

// Now guess the type file's content type based on extension

Note from the Author or Editor:
Please change "the type file's content type" to "the file's content type"

Either "the" or "," seems superfluous in:

"the multiple cores, which"

Note from the Author or Editor:
Change "across the multiple cores" to "across multiple cores"

The word "with" is duplicated:

"...and we saw the same thing with with child processes..."

Note from the Author or Editor:
Please change "with with" to "with"

Appears:

it cannot copy object like SSockets and Streams. It can handle MessagePort objects.

Change to be done:

SSockets => Sockets (remove one of the two "S" at the beginning of the word)

Note about lack of uniformity in those names: in this line, "Sockets" and "Streams" appear with initial "S" (uppercase). The line before that one makes reference to the last paragraph of 16.11.1, in page 628, where that words appear as:

... such as sockets and streams. ...

(with initial lowercase in both words). This line is the 3rd line of that paragraph.

Note from the Author or Editor:
Please change "SSockets and Streams" to "sockets and streams".

Original: The postMessage() function uses the structured clone algorithm, and as we’ve noted, it cannot copy objects like SSockets and Streams.

Issue: SSockets

Suggestion: The postMessage() function uses the structured clone algorithm, and as we’ve noted, it cannot copy objects like Sockets and Streams.

Note from the Author or Editor:
Please change "SSockets" to "Sockets"

"with" seems superfluous in:

// Now create a worker thread, passing the shared array to it with

Note from the Author or Editor:
Please remove "with" at the end of that code comment

Original: "Prettier for formatting your JavaScript code in a standardized way."

Issue: "Unnecessary "for" after "Prettier".

Note from the Author or Editor:
Most of the bullets begin with a tool name and "Prettier" is the name of the tool, so if you already know that Prettier is the name of a tool, then the sentence reads naturally as it is.

But I see now that if you have never heard of Prettier, then this looks like a typo.

Let's change "Prettier for formatting" to "The Prettier tool for formatting"

maybe "best...than" => "better...than" or "best...rather than"

Note from the Author or Editor:
Change "user experience is best" to "user experience is better"

Original: "Babel was created so that web developers could use the new language features of ES6 and later while still targeting web browsers that only supported ES5."

Issue: This sentence seems a little outdated. It might be helpful to point out that Babel also supports current developments in ES2020, etc.

Suggestion: "Babel was initially created so that web developers could use the new language features of ES6 and later while still targeting web browsers that only supported ES5. It is under constant development to also support current and future versions of the EcmaScript standard."

Note from the Author or Editor:
This is a good idea. Please add the following sentence after "...while still targeting web browsers that only supported ES5.":

Babel continues to evolve, and it is common for language feature that are nearing standardization to be supported by Babel before they are implemented natively in browsers.

"feature" should be "features" in the sentence to be added: "Babel continues to evolve, and it is common for language feature..."

"use use" => "use"

"name" => "names"

maybe "types" => "type" in:

"the type of the keys and the types of the values"

Note from the Author or Editor:
Please change "the types of the values" to "the type of the values"

Original: "To express the type of a function with Flow, write the types of each parameter, separate them with commas, enclose them in parentheses, and then follow that with an arrow and type return type of the function."

Issue: The last part ("…and type return type of the function.") of the sentence is unclear.

Did you mean, "…and **the** return type…"?

Note from the Author or Editor:
Please change "type return type" to "the return type"