Fixing the Expected an assignment or function call and instead saw an expression Error in React Menu

A common issue faced by React developers is the error stating `Expected an assignment or function call and instead saw an expression`. Learn how to solve this problem while building your side navigation menus!
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Understanding the React Menu Error

If you're new to React, running into errors like "Expected an assignment or function call and instead saw an expression" can be frustrating. This error typically occurs due to incorrect JavaScript syntax. In this guide, we'll explore this error in the context of building a side menu navigation using the antd library, and learn how to fix it effectively.

The Problem

You were attempting to build a side menu navigation and stored the key and labels in an array. However, while trying to render this array, you encountered the following error on line 41 of your code:

[[See Video to Reveal this Text or Code Snippet]]

This error was highlighted at the part of your code where you were trying to use the forEach method incorrectly. Let's see what went wrong.

The Cause of the Error

1. Incorrect Syntax Usage

In your code, you used the forEach method which is designed for executing a function on each array element without returning any values. Therefore, when you try to pass the result of forEach to the items property in the <Menu> component, it leads to the mentioned error.

2. Using Curly Braces for Object Literal in Arrow Functions

Additionally, when you used the arrow function like this:

[[See Video to Reveal this Text or Code Snippet]]

The {} braces are being recognized as the beginning of a function body, leading to the error.

The Solution

In order to solve this, there are two key changes you need to make:

1. Switch from forEach to map

You should use the map function instead of forEach because map creates a new array by applying a function to each element in the array, which is necessary for what you're trying to achieve.

2. Properly Format Your Arrow Functions

You need to ensure that when you define an object in an arrow function with braces, it is wrapped in parentheses to avoid being treated as a function body.

Here's how your corrected code should look:

[[See Video to Reveal this Text or Code Snippet]]

Note on Simplification

Interestingly, if your code logic was intended as shown, and if all you're doing is copying the properties into a new object with the same keys and values, you can simplify your code even more. Instead of mapping the objects into new objects that contain the same values, you can simply do the following:

[[See Video to Reveal this Text or Code Snippet]]

This directly passes your original array of menu items to the Menu component.

Conclusion

Encountering errors like "Expected an assignment or function call and instead saw an expression" can be common when starting out with React. By understanding how to properly use array methods like map, and knowing how to handle object literals within arrow functions, you can navigate these issues more effectively.

Keep experimenting, and don't get discouraged—errors are just stepping stones on your path to mastering React! Happy coding!