javascript

CHAPTER 1 ■ REPRESENTING DATA WITH VALUES
14
To update the value of a member or to add a new member, you would use the = operator, same as
before. Let’s add a bostonCreamPie member to iceCream. Then query its value, verifying our work with
Figure 1–10:
var iceCream = {
chocolateFudgeBrownie: 4 * 260,
halfBaked: 4 * 270,
newYorkSuperFudgeChunk: 4 * 300,
coffeeHeathBarCrunch: 4 * 280,
cherryGarcia: 4 * 240,
mudPie: 4 * 270,
milkCookies: 4 * 270,
cinnamonBuns: 4 * 290,
chocolateChipCookieDough: 4 * 270,
missionToMarzipan: 4 * 260
};
iceCream.bostonCreamPie = 4 * 250;
iceCream.bostonCreamPie + " calories per pint";
// "1000 calories per pint"
Figure 1–10. Writing a new value to a member named with an identifier
Creating an Array Literal
The members in iceCream are coded like a top-ten list. However, there’s no way to have JavaScript query
them that way. We couldn’t ask, “What’s my third favorite flavor?” for example. Plus, we have to name
members and give them a value.
So, if we wanted to simply create a top-ten list of flavors, omitting the depressing calorie details, an
object wouldn’t do. For that we’d need an array, which is a subtype of the object value type. That is to
say, an array is still an object; it just has some additional features.
One of those features is ordering values numerically with non-negative integers beginning at 0.
JavaScript does so behind the scenes. So, you just list values in an array from first to last; JavaScript takes
care of the numbering. Note that numbered values are referred to as elements rather than members.