Vue.js Error: Uncaught TypeError: Cannot read properties of undefined (reading 'header') - Troubleshooting and Solutions - 常规

This error, 'Uncaught TypeError: Cannot read properties of undefined (reading 'header')', signals that your code attempts to access the 'header' property from an object that is undefined. This could stem from various scenarios:

Uninitialized object: You might be trying to access a property of an object that hasn't been properly initialized or created yet.
Undefined object passed as argument: A function might be expecting a defined object as input, but instead receives an undefined value.
Typo in the property name: A simple misspelling in the property name ('header') can lead to this error.

Debugging Steps:

Locate the error: The error message will usually point to the file and line number where the error occurs. Examine the code at that location.
Identify the undefined object: Determine which object is being accessed with the 'header' property. Check if it's truly defined at that point in your code. If it's expected to be initialized later, ensure the initialization happens before trying to access its properties.
Inspect function arguments: If the error occurs within a function, carefully inspect the function call and verify that the object being passed in is actually defined.
Double-check property names: Carefully review the property name ('header') to rule out typos or case-sensitivity issues.

Example Scenario:

Let's imagine you have a component that uses the 'vuedraggable' library and tries to access the 'header' property of a dragged element. The error might occur if the dragged element is initially undefined or hasn't been properly set up yet. To fix this, you would ensure that the dragged element is correctly initialized before attempting to access its 'header' property.

Additional Resources:

Vue.js Documentation: https://vuejs.org/
Vuedraggable Documentation: https://github.com/SortableJS/Vue.Draggable
JavaScript Error Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors

By understanding the error and following these debugging steps, you can effectively troubleshoot and resolve this 'Uncaught TypeError: Cannot read properties of undefined (reading 'header')' error in your Vue.js application.