ActionScript: The Definitive Guide

Creating and Categorizing Data

There are two ways to create a new datum with ActionScript, both methods requiring the use of expressions—phrases of code that represent data in our scripts.

A literal expression (or literal for short) is a series of letters, numbers, and punctuation that is the datum. A data literal is a verbatim description of data in a program’s source code. This contrasts with a variable, which is a container that merely holds a datum. Each datatype defines its own rules for the creation of literals. Here are some examples of literals:

"loading...please wait"  // A string literal
1.51                     // A numeric literal
["jane", "jonathan"]     // An array literal

Note that movie clips cannot be represented by literals, but are referred to by instance names.

We can also generate data programmatically with a complex expression. Complex expressions represent data as a phrase of code with a value that must be calculated or computed, not taken literally. The calculated value is the datum being represented. For example, each of these complex expressions results in a single datum:

1999 + 1       // Yields the datum 2000
"hi " + "ma!"  // Yields the datum "hi ma!"
firstName      // Yields the value of the variable firstName
_currentframe  // Yields the frame number of the playhead's current position
new Date( )     // Yields a new Date object with the current date and time

Notice that an individual literal expression like 1999 or 1 can be a valid part of a larger complex expression, as in 1999 + 1.

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