Solutions that can be used to debug JavaScript errors _ javascript skills

Some js Errors often occur during js writing. The following article describes the relevant debugging methods as the key to solving the errors. A uses the alert () and document. write () methods to monitor variable values.
If you want to interrupt code execution and monitor variable values, use the alert () method;
If you want to view a large number of values, use the document. write () method to avoid repeated clicking the "OK" button;

B. Use the window. onerror event
When an exception occurs on the page, the onerror event is triggered on the window object. It can tell developers related error information to a certain extent.
Example:

The Code is as follows: