Design Patterns

■INDEX 265
deliver method, 219
dependencies, hard-coded, 249
dequeue, 114
design patterns. See patterns
DHTML, 144–145
dialog boxes, flyweight pattern for, 190–192
directory lookup (example), 206–210
display method, 27–29
DOM elements, reducing needed, 186–190
duck typing, emulating interfaces with,
17–18
dynamic implementations, 99
dynamic user interface, 225–226
dynamic virtual proxy, creating, 210–213
E
edit-in-place field (example), 52
using classical inheritance, 52–55
using mixin classes, 59–62
using prototypal inheritance, 55–58
efficiency, of virtual proxies, 213
email API, adapter pattern with, 152–158
encapsulation
benefits of, 39
defined, 26
drawbacks of, 39–40
vs. information hiding, 26
inheritance and, 49–50
encapsulation functions, 226–227, 243
ensureImplements function, 18
event bubbling, 255
event capturing, 255
event delegation, 122, 255
event listeners
with bridge pattern, 109–110
as observers, 222
use of, in JavaScript, 142
event objects, 255
event utility, creating with facade pattern,
146–147
event-driven environments, 215
execute method, 226, 229, 235–239
extend function, 43–45, 55, 62
extend keyword, 42
externally hosted libraries, 20
extrinsic data, 179, 192
encapsulation of, 182–183
removing from class, 188–189
storage of, 186, 193
extrinsic state, 180–186
F
facades/facade pattern, 201
vs. adapter pattern, 144, 149
addEvent function, 142, 146–147
benefits of, 148
vs. bridges, 111
common examples of, 141–142
as convenient methods, 143–144
creating event utility (example), 146–147
drawbacks of, 148
introduction to, 141
JavaScript libraries as, 142
setting styles on HTML elements
(example), 144–145
steps for implementing, 147
uses of, 141, 148
factory method, changing function into, 84
factory pattern, 23, 38, 83
benefits of, 107
creating decorator objects with, 169–172
creating, for flyweight pattern, 193
drawbacks of, 108
example, 99–104
instantiation using, 181
RSS reader (example), 104–107
simple, 93–96
true, 96–98
uses of, 99
fieldsets, 128
findProduct function, 67
flyweight manager, 193
flyweight pattern
calendar (example), 185–186
car registrations (example), 179–183
composite pattern with, 183–186
converting objects to, 185
drawbacks of, 194
encapsulation of extrinsic data, 182–183
extrinsic state and, 180–186
for dialog boxes, 190–192
instantiation using a factory, 181
intrinsic state and, 180–181
introduction to, 179
steps for implementing, 193
storing instances for reuse, 190–192
structure of, 179
tooltip objects (example), 186–190
web calendar (example), 183–185
when to use, 192
fooMail, migrating to dedMail from, 157–158
form elements, 127–128
form validation, using composite pattern,
127–136
FormItem interface, 128, 133
fully exposed objects, 27–30
functions
combining, with facades, 143–144
convenience, 143–144
decorator pattern for, 172–173
as first-class objects, 6–8
in JavaScript, 6–8
modifying into factory method, 84
nested, 32–33, 36