Javascript callbacks

gistfile1.js

/*
  Why does the first function work properly but the second does not? The second one fails
  because the file variable does not get properly passed to testExt.
*/

/* Example 1 */
function listFiles(err, files) {
  if (err) throw err;
	files.forEach(function (file) {testExt(file);});
}


/* Example 2 */
function listFiles(err, files) {
  if (err) throw err;
	files.forEach(testExt(file));
}

Well, forEach expects a function callback. In the first example, you correctly pass a function object (or pointer if you prefer). In the second example, the testExt(file) function is called once when the line is reached and the result of the call to testExt(file) is then "called" for each file in the array. Of course, if testExt(file) doesn't return a function object then you will get errors. Also, in the second example the file variable is not defined.