'TypeError: Cannot set property 'xxx' of null' in Vue application - how to solve it?

The Vue framework is a modern JavaScript application framework that is widely used in Web development. During the development of Vue applications, we may encounter some error messages, such as "TypeError: Cannot set property 'xxx' of null". This article explains what this error message means, why it occurs, and how to resolve it.

What is the "TypeError: Cannot set property 'xxx' of null" error?

When we use components in Vue applications, we may encounter the following error message:

Uncaught TypeError: Cannot set property 'xxx' of null

This appears The error is usually triggered when we try to set properties on an object or variable that does not exist.

Specifically, in a Vue component, we may use the $data attribute to access the component's data, as shown below:

this.$data.xxx = 'some value';

If the component's data has not been defined or initialized before, then the "Cannot set property 'xxx' of null" error will be triggered because the $this.$data object itself is null.

The essence of this error message is a JavaScript reference error. We need to find the line of code where this error occurs, identify which variable or object has a null value based on the error message, and then adjust our code to avoid this mistake.

How to solve the "TypeError: Cannot set property 'xxx' of null" error?

Through the above analysis, we can see that the "TypeError: Cannot set property 'xxx' of null" error usually appears in the following situations:

1. The access does not exist or does not exist Defined object or variable

If we access an object or variable that has not been initialized or defined, we will get this error. The solution is to initialize or define the object or variable before using it.

2. Accessing an object that has been destroyed

When we try to access an object that has been destroyed, such as accessing a JavaScript object in a closed window, it will This error occurs. The solution is to avoid accessing the object after it has been destroyed.

3. Calling a method that does not exist

If we call a method that does not exist, this error will occur. The solution is to confirm that the method exists and that it is referenced correctly.

Summary

In a Vue application, when we encounter the "TypeError: Cannot set property 'xxx' of null" error, we need to analyze the source of the error message and determine which object or The value of the variable is null, and then the code is adjusted. Avoiding access to undefined objects or variables, avoiding access to objects that have been destroyed, and referencing methods correctly are all common ways to resolve this error.

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