Resolve TypeError: Cannot Read Properties of Undefined (reading 'get')

Understand why "typeerror: cannot read properties of undefined (reading 'get')" error occurs, look at real examples of the offending line, and go through step-by-step ways to fix and prevent the same error from occurring in your future projects.

You’re testing your JavaScript code, everything looks fine, and then—suddenly—the console flashes:

“Uncaught TypeError: cannot read properties of undefined (reading 'get')”.

The application stops, the page breaks, and you’re left staring at the error message, wondering what went wrong. If this feels familiar, you’re not alone—this is one of the most common runtime issues developers face.

This happens when the script attempts to read properties of undefined, meaning the variable or object you expected to hold a valid value was never initialized or assigned properly. The result is an uncaught TypeError that halts execution and often leads to debugging frustration.

What Does “Cannot Read Properties of Undefined Reading get” Mean?

This error message is generated when JavaScript attempts to read properties of undefined. In simpler terms, your script expects an object or variable to exist, but it has not been initialized or assigned a valid value. The browser then throws an uncaught TypeError since it cannot proceed with executing the function that depends on the missing object type.

When the offending line is reached in your script, the interpreter fails to access the method or property and halts execution.

Common Situations Where This Error Appears

There are multiple ways this issue may occur in projects. Let’s go through the most frequent scenarios:

1. Undefined variable access

   A variable is referenced before being assigned any value.

2. Event object not initialized

   When working with browser events, the event object may not be passed properly to the function, leading to an uncaught TypeError.

3. Invalid object structure

   When the structure of the data differs from what is expected, for example, API calls may return null or incomplete JSON, leading to the following error.

4. Improper array or object access

   Trying to read an element from an array or nested object that does not exist.

Identifying the Root Cause in JavaScript

To fix the error, you must identify the exact offending line where the code is trying to read property values. Use the browser console or Node.js log statements to trace the variables.

For example:

Copy
1console.log(userData);
2console.log(userData.get);
3

The logs will reveal whether the object is initialized or still undefined. Once you identify the line, you can fix the script by adding if check statements or optional chaining operators.

Example of Wrong Code Leading to the Error

The above code shows how a missing initialization causes problems:

Copy
1let user;
2console.log(user.get("name")); // TypeError: Cannot read properties of undefined (reading 'get')
3

In this example, the variable user is not assigned any valid value, leading to an error.

Fixing the Same Error with Initialization

You can correct the same error by properly assigning an object before calling its method:

Copy
1let user = new Map();
2user.set("name", "Alex");
3console.log(user.get("name")); // Works fine
4

Here, the variable is initialized as an object before being accessed.

A detailed discussion on this error can be found in the Flutter GitHub issue #90340 , where developers share insights and debugging steps. It highlights real-world cases of typeerror cannot read properties of undefined (reading 'get') and potential fixes.

Using Conditional Checks to Avoid the Error

A reliable way to prevent such errors is by adding validation in the script.

Copy
1if (user && typeof user.get === "function") {
2  console.log(user.get("name"));
3}
4

This if check makes sure the variable exists and has the expected function before accessing it.

Applying Optional Chaining

Modern JavaScript provides optional chaining, which reduces repetitive checks.

Copy
1console.log(user?.get?.("name"));
2

If the object or function is not available, the script will return undefined instead of throwing an uncaught TypeError.

Common Mistakes That Trigger the Error

The error often occurs due to:

• Forgetting to pass the event object in functions handling browser events.
• Accessing a property of an object before it is properly initialized.
• Wrong API response structure with missing values.
• Attempting to read from a null or undefined variable.

The above example of missing initialization highlights how a small mistake can stop scripts from executing.

Debugging and Best Practices

Debugging JavaScript scripts requires a clear process to track the offending line and resolve the issue quickly. When the browser shows an error message like “cannot read properties of undefined”, the problem usually comes from a variable or object that is not properly initialized.

1. Use console.log to Trace Variables

Insert console.log() before the failing line to check the value, object type, or whether the variable is undefined.

Copy
1console.log(userData);
2console.log(userData?.get);
3

This reveals if the script is trying to read property values from a missing object.

2. Check File and Line Number

Most error messages indicate the exact file and line where the issue occurs. Reviewing that part of the script helps you spot misnamed variables, missing functions, or other small mistakes.

3. Validate API Responses and Data Structures

APIs often return unexpected data. Always confirm the response body has the expected properties before accessing them:

Copy
1if (response && response.user) {
2  console.log(response.user.get("name"));
3}
4

4. Use Conditional Checks or Optional Chaining

Add an if check before calling a function or reading a property:

Copy
1if (user && typeof user.get === "function") {
2  console.log(user.get("name"));
3}
4

Or use modern optional chaining:

Copy
1console.log(user?.get?.("name"));
2

By combining logs, data validation, and safe access methods, developers can prevent repeated uncaught typeerror issues and make their scripts more reliable.

Handling Errors in Real-World Applications

In real projects, the error message can break user-facing HTML pages or API scripts. A professional developer should:

• Always validate inputs from users.
• Implement error-handling methods in functions.
• Prevent uncaught TypeError by validating objects before calling functions.
• Log meaningful statements to debug issues faster.

For instance, while handling events, pass the event object explicitly to avoid unexpected failures.

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Preventing the Error in Arrays and Objects

Arrays and objects often cause unexpected issues:

Copy
1let data = [];
2console.log(data[0].name); // Cannot read property 'name' of undefined
3

To fix this:

Copy
1if (data[0]) {
2  console.log(data[0].name);
3}
4

Here, you are validating whether the array item exists before accessing its property.

Avoiding the Same Error with API Data

When working with APIs, the body of the response may not have the expected properties.

Copy
1fetch("/api/data")
2  .then(res => res.json())
3  .then(result => {
4    console.log(result.user.get("name")); // Might fail
5  });
6

Instead, always log the object and add if checks or optional chaining before accessing.

Final Thoughts

The root cause of this error lies in trying to access or call a method on an undefined object or variable. By analyzing the offending line, adding validation, and adopting optional chaining, you can prevent such issues from affecting your application.

Understanding how to handle uncaught TypeError scenarios properly ensures more reliable JavaScript code execution, and it saves valuable debugging time for every developer.