Learning to Program

Catch When Things Go Wrong

You might be wondering why you would want to be writing risky instructions in the first place. What makes an instruction risky? Remember in Chapter 2, “How Software Works,” we wrote some fake code to open a Microsoft Word document? See Listing 7.30 for a refresher. That code is actually quite risky.

Listing 7.30 Open a Microsoft Word Document (Example from Chapter 2)

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function openWordFile(filePath) {  var wordWindow = openWordWindow();  var fileContents = loadFile(filePath);  displayFile(wordWindow, fileContents);}

The risky part of that code is loadFile(filePath). What if the file path isn’t valid? What if the file was deleted? What if the file path points to an external hard drive that ...