HTML and CSS Reference
In-Depth Information
This section contains the solutions to the thought experiments and answers to the objective
review questions in this chapter.
Objective 2.1: Thought experiment
Writing clean JavaScript comes with some clear advantages. Choosing the correct construct to
handle a problem is imperative to achieving the goal of clean script.
A for loop and while loop can both get the same jobs done interchangeably, but some se-
mantic differences make one more preferable over the other in various situations. When you
know how many times a loop must run, the for loop is ideal. It has all the built-in semantics
to handle a counter to iterate a known number of times. It can be replaced with a while loop,
but the while loop requires extra variables and code added to the loop to take care of the
counting of the number of times the loop runs.
The while loop is better when you don't know the number of times a loop will run; it's
indeterminate. This is where the loop runs until the logic within the loop achieves a certain
state; hence, why the while loop evaluates on a Boolean expression.
You can apply the same logic when choosing between an if statement and a switch state-
ment. Although a switch statement can easily be replaced by an if statement, the inverse isn't
true. Checking single values for equality in an if…else construct can become long and cum-
bersome. if statements allow for more complex evaluations, including compound evaluations
using AND and OR logic. s witch statements are more useful for evaluating a single value
against a long list of possible values such as enumeration. Choosing the correct construct for
the problem is imperative to readable and maintainable script.
Objective 2.1: Review
Correct answer: C
Incorrect: The if statement provides branch flow control.
Incorrect: The switch statement provides branch flow control.
Correct: The for loop provides iterative flow control.
Incorrect: The break keyword is used to exit an iterative control block such as a for
or while loop.
Correct answer: D
Incorrect: The join method joins all the elements of an array into a string.
Incorrect: combine isn't a valid method.
Incorrect: The split method is used to split a string into an array of substrings.
Correct: The concat method combines the elements of two arrays into one array.
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