JavaScript error handling and debugging experience _ javascript skills

During Web development, JavaScript programs may encounter various errors such as syntax errors and logic errors. For a short piece of code, you can check carefully to eliminate the error. However, if the program is a little complicated, debugging JS becomes a headache for Web developers. The following describes how to handle and debug JS errors.
Method 1: Use the alert () and document. write () methods to monitor variable values.
When the variable value is displayed in the pop-up dialog box, alert () stops running the code until the user clicks "OK", while the document. write () continues to run the code after the output value. This method can be selected based on the actual situation when debugging JS.
For example, the following code adds data starting with 1 in array a to array B.

The Code is as follows:

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