javascript

CHAPTER 4 ■ CONTROLLING FLOW
So tally < 100 returns false, and JavaScript goes down the else path. Therefore,
mayfly.kmLeftToLive() returns "Mayfly is dead!" to indicate that it’s time to buy a new Mayfly.
By the way, even if you are not a runner, you might want to try the Mayfly sometime. The upper part
is bright orange with a black support grid resembling the wing of a fly—you will be hard to miss in a pair
of those!
To Wrap or Not to Wrap
As noted earlier, whenever a compound statement contains a single child statement, you do not have to
wrap it in curly braces. So, we could have defined mayfly like so, where the bold code shows the single
child statements do not have curly braces:
var mayfly = function () {
var tally = 0;
return {
addToTally: function (km) {
if (typeof km === "number" && isFinite(km))
return tally += km;
else
return "Invalid parameter!";
},
kmLeftToLive: function () {
if (tally < 100)
return "Mayfly has " + (100 - tally) + " kilometers left to live.";
else
return "Mayfly is dead!";
}
}
}();
Furthermore, we could have omitted the line breaks, too:
var mayfly = function () {
var tally = 0;
return {
addToTally: function (km) {
if (typeof km === "number" && isFinite(km)) return tally += km;
else return "Invalid parameter!";
},
kmLeftToLive: function () {
if (tally < 100) return "Mayfly has " + (100 - tally) + " kilometers left to live.";
else return "Mayfly is dead!";
}
}
}();
The else if idiom, which we will cover next, takes advantage of this single-line, no-bracket
JavaScript feature. Moreover, you will encounter both styles in scripts written by others, myself included.
However, as a beginner, you may want to wrap single child statements in curly braces inasmuch as this
eliminates the need for you to remember that two or more child statements need to be wrapped in curly
braces and that an else clause goes with the nearest if condition.
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