ActionScript: The Definitive Guide

The Boolean Type

Boolean data is used to represent the logical states of truth and falsehood. There are, hence, only two legal values of the boolean datatype: true and false. Notice that there are no quotation marks around the words true and false because Boolean data is not string data. The keywords true and false are the reserved primitive data values and may not be used as variable names or identifiers.

We use Boolean values to add logic to the execution of code. For example, we might assign the value true to a variable that tracks the status of a spaceship’s firepower:

shipHasDoubleShots = true;

By comparing shipHasDoubleShots to the Boolean literal true, we can then decide how much damage to inflict when a shot hits its target:

if (shipHasDoubleShots == true) {
  // Shoot them with twice the power.
  // This will be reached if the comparison is true.
} else {
  // Shoot them with a single dose.
  // This will be reached if the comparison is false.
}

When the double-shot power runs out, we can set the variable to false:

shipHasDoubleShots = false;

This will cause the larger expression shipHasDoubleShots == true to become false, causing the single-damage-dose script to execute when a shot hits its target.

All comparison operators express results with Boolean values. When we ask, “Is the user’s guess the same as the password?” the answer is given as a Boolean:

// userGuess == password will yield either true or false
if (userGuess == password) {
  gotoAndStop("secretContent");
}

And when we ask, “Is ...