Today I just would like to list off a simple debugging checklist for you to consider when working on your own programs...
- Ensure parentheses and curly braces match up (code organization helps this)
- Avoid typos, especially in variable/function names
- Be consistent with the use of single and double quote usage
- Use escape characters (\)
- Be careful not to use '=' when you actually mean '=='
- Be certain elements/objects have been created before attempting to use them (undefined error...applies to DOM elements in particular)
- Do not create shadow variables...name global and local variables differently
The aforementioned is a simple, short list, but will go a long way in helping you avoid bugs in your code right from the start....