Table Of Contents
- 2 What is Uncaught TypeError?
- 3 What Causes Uncaught TypeError?
- 4 How to Fix Uncaught TypeError?
- 6 Frequently Asked Questions
HTML: A markup language that provides the structure of a webpage or contents of a webpage. Such as header, footer, images, table, etc.
CSS: Also known as Cascading Style Sheets, CSS is used to style your webpage contents. Such as font, background color, and foreground color. The CSS also provides animations.
Higher Order Functions: The function that returns a function is called a higher-order function, and JS supports higher-order functions.
The problem frequently occurs when the scripts encounter an uninitialized variable or object.
The RangeError object is an error thrown when a value is not in the set or range of allowed values.
- When you try to create an array of illegal lengths using the Array Constructor
- Passing non-allowed values to numeric methods such as toExponential(), toPrecision(), and toFixed()
- Passing non-allowed values to string functions like normalize()
The Reference Error object indicates an error when a variable that doesn’t exist (or hasn’t yet been initialized) in the current scope is referenced.
Example Error Message: ReferenceError: assignment to the undeclared variable “s”
- Typo in the variable name
- When you try to access the variable outside their scopes
- Referencing a global variable from an external library before it is loaded
Example: Uncaught SyntaxError: Invalid or unexpected token
- Missing inverted commas
- Missing Parenthesis, braces
- Illegal usage of special characters
The TypeError occurs when a variable or parameter is not of a valid type.
- Invoking objects that are not methods
- Attempting to access properties of null or undefined objects
- Treating a number as a string or vice versa
URIError: The URIError indicates that the global URI handling function was used in the wrong way.
AggregateError: The Aggregate Error is an error when several errors are wrapped into a single error. The aggregate error is useful when multiple errors need to be reported by an operation.
What is Uncaught TypeError?
The TypeError: Cannot read property of undefined
TypeError: Cannot read properties of undefined (reading x)
What Causes Uncaught TypeError?
Causes for TypeError: Cannot Read Property of Undefined
The error clearly says that it is Undefined, which means the variable might be declared or used. Still, there is no value associated with the variable. In short, the value is not assigned.
Example of Type Error
Let’s understand the TypeError: Cannot read property of undefined
Consider the above example,
var someVar: we have declared the someVar, but there is no value associated with it.
someFunc(someVar): This function call passes the someVar to the someFunc. In our case, the variable someVar doesn’t have any value as we have not assigned it, so by default, it’s undefined.
console.log(x.y): Inside the someFunc(), we have console.log, which is trying to access the value of x that belongs to someVar or y. Since the y is undefined, now if you execute this code, you will get the message TypeError: Cannot read properties of undefined (reading ‘x’)
How to Fix Uncaught TypeError?
The solution to TypeError: Cannot read properties of undefined
- Always conditionally check for the variable that is undefined before accessing the value.
In the above code, we have modified the someFunc() with the if condition, which checks for undefined.
if(y!==undefined): This line of code checks if the variable is undefined or has the value. Since we have added the if condition, if there is no undefined, then only the control moves to the next statement and prints the console; accidentally, if you forget to assign the value, then the if condition validates and doesn’t throw any error.
- Ensure the variable has been assigned a value before accessing them.
The TypeError typically occurs when the variable does not have any assigned value. When you write the code, you must ensure that the variable you pass has a valid assigned value.
You can modify the code as follows:
In the above code, we have assigned the value to someVar, which now has valid values; when you pass it to the someFunc, it doesn’t cause any error.
The code looks like the below:
In the above code, we have assigned the value to the variable, and we are also checking if the passed variable has an undefined value.
- Have a coding standard checklist and make it mandatory for developers before pushing the code to the repository.
- Peer Review greatly helps to avoid any mistakes that developers make. Peer Reviews are also a great way to bring and monitor the standards for your framework.
- If your team has Junior resources or resources with fewer skills, consider Pair Programming. It is the best way to enforce the standards and increase learning.
- Consider Unit Testing is the best way to catch errors or bugs in the early stage. Unit testing also helps in avoiding regressions.
- Have a mechanism to log the error. Logging errors sometimes cause a security risk, but you can log the custom error messages, which helps you to trace back and quickly fix the errors.
The above guidelines can minimize the bugs occurring when delivered but guarantee no future bugs. The only way to eliminate the error is through thorough application testing. Testing is time-consuming and needs more effort if it is done manually. Nowadays, many organizations are moving towards Test Automation since the same code can run on multiple browsers without additional effort. One of the challenges of modern test automation is that many tools are available, and every tool requires expertise. Organizations are spending a lot on upskilling resources. Since testing is moving towards automation, manual testers have difficulties adapting and learning new technologies. Some tools like Testsigma allow testers to write the script in basic English and make it easier to transform the testers.
The Record and playback feature helps beginners to upskill their skillsets rapidly and deliver better. Testsigma understands the pain points of both testers and managers. The tester doesn’t want to spend much time learning; the manager needs faster testing and sound reports to highlight the issues. Testsigma provides Summary Reports, Trends, Automated Bug Reporting, etc., making life easy for managers and stakeholders, while codeless automation makes testers’ lives better.
Frequently Asked Questions
Determine the exact line or section of code where the type error occurs. Look for error messages in your browser’s console, which will show you where the problem is.
Examine the data types of the variables or values in the code. Check that they are compatible and of the expected types.
To ensure that the correct types are used, use type-checking methods or functions. You can, for example, use the typeof operator to determine the type of a variable before performing operations on it.
To track the flow of execution and identify any unexpected type conversions or assignments, use console.log statements or a debugger tool.
What is Uncaught Type Error Not a Function?
What is Uncaught Syntax Error?