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Exercise 2

What do the following error message and stack trace tell you?

$ node exercise2.js
/Users/wolfy/tmp/exercise2.js:4
  console.log(greeting);
              ^

ReferenceError: greeting is not defined
    at hello (/Users/wolfy/tmp/exercise2.js:4:15)
    at Object.<anonymous> (/Users/wolfy/tmp/exercise2.js:13:1)
    at Module._compile (internal/modules/cjs/loader.js:721:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)
    at Module.load (internal/modules/cjs/loader.js:620:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:560:12)
    at Function.Module._load (internal/modules/cjs/loader.js:552:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:774:12)
    at executeUserCode (internal/bootstrap/node.js:342:17)
    at startExecution (internal/bootstrap/node.js:276:5)

Solution

An error occurred in the exercise2.js program on line 4 of the program; a ^ points to where JavaScript thinks the error is in the code: it's pointing to the argument list for console.log.

More specifically, line 6 in the output tells you that a ReferenceError exception occurred and that the name greeting isn't defined. Line 7 repeats some earlier information: JavaScript detected the error at column 15 of line 4 of the program, but it also tells you that the code is in the hello function. Line 8 tells you that hello was called from line 13 of the program in an anonymous function, namely the global-level of the program.

The rest of the output comes from running the code in node and probably isn't useful to you as an application programmer.

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