Learning to Program

Variables

You already know that a variable is used to store some data that is to be used at some point in the program. Variables are one of the most important tools in a programming language. A variable really can vary, which is why it is so useful. When you play a video game (such as Mario Bros. 3), your score is saved to a variable. When you start a new game, the variable is set to 0, and each time you score points, the value of the variable increases (see Listing 2.9).

Listing 2.9 Keeping Score with Variables

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var score = 0;// Increase the score by the amount given in pointsfunction increaseScore(points) { score = score + points;}

The player’s score is stored in a variable called score. In JavaScript, you use ...