Software such as Visual Studio (C++, VB, C#) incorporate great debuggers which alert the programmer to an error. Often they also provide the exact location as well as possible suggestions. This is not the case with JavaScript. Chapter 4 provides some tools such as the console debugger to assist with assuring code is error free.

One might be tempted to not devote a sufficient amount of time to the information related to the console debugger. As the course progresses and code becomes more involved you appreciate the effort that was made at this point in the course. As the saying goes "Pay now or pay later!"

Make it your goal this week to become proficient in debugging techniques that can be used for this course and all future JavaScript coding.

P. 271

The text provides an example of adding an event listener for errors. Now this may a raise a question about calling more than one function when a page loads. An option might be as shown below for SetUpPage() and CreateListeners(). The code for attachEvent() would be similar.

window.addEventListener("load",function(){setUpPage();createEventListeners();});;

Keep in mind that parameters can be passed to these functions using the following format.
Note: the following should be all on one line.

document.getElementById("btnListLength").addEventListener("click", function() {createList(document.forms[0].listLength.value);});;

Also keep in mind that when an element is going to be accessed more than one time, it might be wise to store the value in a variable. The last line of code could be modified as follows:

var buttonList = document.getElementById("btnListLength");
var listItemLength = document.forms[0].listLength;
buttonList.addEventListener("click", function() {createList(listItemLength.value);});;

This week's assignments will not cover all of the aspects of error handling. In Chapter 6: Enhancing and Validating Forms, the error trapping will receive additional attention.