Errata

I am unable to determine page number as Safari Books doesn't show page numbers.

you have a mysterious line of code in the example for Observer pattern which is simply:

i.e

Commenting the line out above allows code to run. And while I have your attention, there is a grammatical error:

"Stores a reference to the ConcreteSubject, implements an update interface for the Observer to ensure state is consistent with the Subject?s" is missing punctuation. It runs on to next sentence which doesn't make sense.

I think there is a mistake in the following jQuery example:

function library( module ) {

$( function() {
if ( module.init ) {
module.init();
}
});

return module;
}

var myLibrary = library(function () {

return {
init: function () {
// module implementation
}
};
})();

The argument of the library function should be the new created library, so probably it should be:

function library( module ) {

$( function() {
if ( module.init ) {
module.init();
}
});

return module;
}

var myLibrary = library((function () {

return {
init: function () {
// module implementation
}
};
})());

Or alternatively:

function library( module ) {

$( function() {
if ( module.init ) {
module.init();
}
});

return module;
}

var myLibrary = library(function () {

return {
init: function () {
// module implementation
}
};
}());

The potential errors are located at https://addyosmani.com/resources/essentialjsdesignpatterns/book/#detailflyweight

Here is the code on the webpage:

"function testFlyweight(){


// The flavors ordered.
var flavors = new CoffeeFlavor(),

// The tables for the orders.
tables = new CoffeeOrderContext(),

// Number of orders made
ordersMade = 0,

// The CoffeeFlavorFactory instance
flavorFactory;

function takeOrders( flavorIn, table) {
flavors[ordersMade] = flavorFactory.getCoffeeFlavor( flavorIn );
tables[ordersMade++] = new CoffeeOrderContext( table );
}"

However, should flavors and tables be assigned arrays instead of assigning them "new CoffeeFlavor()" and "new CoffeeOrderContext()" like in the code? Shouldn't it be:

var flavors = []
and tables = []
?

Because "new CoffeeFlavor()" returns an object with methods getFlavor and serveCoffee, and "new CoffeeOrderContext()" returns an object with the method getTable. But in the code we see "flavors[ordersMade]" and "tables[ordersMade++]," where ordersMade is a number, originally assigned 0 (see code "ordersMade = 0,") which seems to only make sense if flavors and tables are arrays...

I might be wrong, but when I ran the linked jsperf comparing getElementsByClassName and querySelectorAll, querySelectorAll was much faster: https://jsperf.com/getelementsbyclassname-vs-queryselectorall/5

However, the text states that getElementsByClassName is far faster.

Since you're talking about the facade pattern and jQuery use abstracting away this performance consideration, it's not a big deal, though vanilla JS gurus might do a double-take.

publicProperty: "I am also public"

needs a trailing comma.


publicProperty: "I am also public",

Here is the code on page 101 and 102 as well as on the webpage:

"function testFlyweight(){


// The flavors ordered.
var flavors = new CoffeeFlavor(),

// The tables for the orders.
tables = new CoffeeOrderContext(),

// Number of orders made
ordersMade = 0,

// The CoffeeFlavorFactory instance
flavorFactory;

function takeOrders( flavorIn, table) {
flavors[ordersMade] = flavorFactory.getCoffeeFlavor( flavorIn );
tables[ordersMade++] = new CoffeeOrderContext( table );
}"

However, should flavors and tables be assigned arrays instead of assigning them "new CoffeeFlavor()" and "new CoffeeOrderContext()" like in the code? Shouldn't it be:

var flavors = []
and tables = []
?

Because "new CoffeeFlavor()" returns an object with methods getFlavor and serveCoffee, and "new CoffeeOrderContext()" returns an object with the method getTable. But in the code we see "flavors[ordersMade]" and "tables[ordersMade++]," where ordersMade is a number, originally assigned 0 (see code "ordersMade = 0,") which seems to only make sense if flavors and tables are arrays...

For the Flyweight coffee example, there's incorrect code on github and in the print book, but corrected code on addyosmani.com--

uncorrected on github and in print book:

https://gist.github.com/addyosmani/2668755

"getCoffeeFlavor: function (flavorName) {

var flavor = flavors[flavorName];
if (flavor === undefined) {
flavor = new CoffeeFlavor(flavorName);
flavors.push([flavorName, flavor]);
}
return flavor;
},"

corrected code located online at https://addyosmani.com/resources/essentialjsdesignpatterns/book/#detailflyweight

getCoffeeFlavor: function (flavorName) {

var flavor = flavors[flavorName];
if (typeof flavor === "undefined") {
flavor = new CoffeeFlavor(flavorName);
flavors[flavorName] = flavor;
length++;
}
return flavor;
},

*I updated this report with a bit more code:

For the Flyweight coffee example, there's incorrect code on github and in the print book, but corrected code on addyosmani.com--

uncorrected on github and in print book:

https://gist.github.com/addyosmani/2668755


"function CoffeeFlavorFactory() {
var flavors = [];

getCoffeeFlavor: function (flavorName) {

var flavor = flavors[flavorName];
if (flavor === undefined) {
flavor = new CoffeeFlavor(flavorName);
flavors.push([flavorName, flavor]);
}
return flavor;
},"

corrected code located online at https://addyosmani.com/resources/essentialjsdesignpatterns/book/#detailflyweight

"function CoffeeFlavorFactory() {
var flavors = {},
length = 0;

getCoffeeFlavor: function (flavorName) {

var flavor = flavors[flavorName];
if (typeof flavor === "undefined") {
flavor = new CoffeeFlavor(flavorName);
flavors[flavorName] = flavor;
length++;
}
return flavor;
},"