const
hand
=
[
randFace
(),
randFace
(),
randFace
()];
for
(
let
i
=
0
;
i
<
hand
.
length
;
i
++
)
console.log(
`Roll
${
i
+
1
}
:
${
hand
[
i
]
}
`
);
Useful Control Flow Patterns
Now that you know the basics of control flow constructs in JavaScript, we turn our
attention to some of the common patterns that you’ll encounter.
Using continue to Reduce Conditional Nesting
Very often, in the body of a loop, you’ll only want to continue to execute the body
under certain circumstances (essentially combining a loop control flow with a condi‐
tional control flow). For example:
while
(
funds
>
1
&&
funds
<
100
) {
let
totalBet
=
rand
(
1
,
funds
);
if
(
totalBet
===
13
) {
console
.
log
(
"Unlucky! Skip this round...."
);
}
else
{
// play...
}
}
This is an example of nested control flow; inside the body of the
while
loop, the bulk
of the action is inside the
else
clause; all we do inside the
if
clause is to call
console.log
. We can use
continue
statements to “flatten” this structure:
while
(
funds
>
1
&&
funds
<
100
) {
let
totalBet
=
rand
(
1
,
funds
);
if
(
totalBet
===
13
) {
console
.
log
(
"Unlucky! Skip this round...."
);
continue
;
}
// play...
}
In this simple example, the benefits aren’t immediately obvious, but imagine that the
loop body consisted of not 1 line, but 20; by removing those lines from the nested
control flow, we’re making the code easier to read and understand.
Using break or return to Avoid Unnecessary Computation
If your loop exists solely to find something and then stop, there’s no point in execut‐
ing every step if you find what you’re looking for early.
For example, determining if a number is prime is relatively expensive, computation‐
ally speaking. If you’re looking for the first prime in a list of thousands of numbers, a
naive approach might be:
76 | Chapter 4: Control Flow
