Error Typeerror: Cannot Read Property 'nativeelement' of Undefined
JavaScript Errors and How to Fix Them
JavaScript tin can be a nightmare to debug: Some errors it gives can exist very difficult to sympathise at first, and the line numbers given aren't always helpful either. Wouldn't it be useful to have a list where you could wait to find out what they mean and how to prepare them? Here you get!
Below is a list of the foreign errors in JavaScript. Different browsers tin can give you unlike letters for the same error, and so there are several dissimilar examples where applicable.
How to read errors?
Before the listing, let'due south quickly await at the construction of an error message. Understanding the structure helps understand the errors, and you'll have less trouble if you run across whatsoever errors non listed here.
A typical error from Chrome looks like this:
Uncaught TypeError: undefined is not a role
The structure of the error is as follows:
- Uncaught TypeError: This part of the message is commonly not very useful. Uncaught means the mistake was non defenseless in a
catchargument, andTypeErroris the fault's name. - undefined is not a office: This is the bulletin part. With fault messages, yous have to read them very literally. For example in this case it literally means that the code attempted to use
undefinedlike it was a function.
Other webkit-based browsers, like Safari, requite errors in a similar format to Chrome. Errors from Firefox are similar, only do non always include the commencement role, and contempo versions of Internet Explorer also give simpler errors than Chrome – merely in this example, simpler does non e'er hateful improve.
Now onto the bodily errors.
Uncaught TypeError: undefined is not a office
Related errors: number is non a function, object is not a function, cord is not a function, Unhandled Error: 'foo' is not a function, Function Expected
Occurs when attempting to call a value similar a role, where the value is not a role. For example:
var foo = undefined; foo();
This error typically occurs if yous are trying to phone call a office in an object, merely y'all typed the name wrong.
var 10 = document.getElementByID('foo'); Since object properties that don't be are undefined past default, the above would result in this error.
The other variations such as "number is non a part" occur when attempting to telephone call a number similar information technology was a part.
How to fix this error: Ensure the function name is right. With this error, the line number will ordinarily point at the correct location.
Uncaught ReferenceError: Invalid left-hand side in consignment
Related errors: Uncaught exception: ReferenceError: Cannot assign to 'functionCall()', Uncaught exception: ReferenceError: Cannot assign to 'this'
Caused by attempting to assign a value to something that cannot be assigned to.
The almost common example of this mistake is with if-clauses:
if(doSomething() = 'somevalue')
In this example, the developer accidentally used a unmarried equals instead of ii. The message "left-paw side in consignment" is referring to the part on the left side of the equals sign, so like you tin see in the above example, the left-hand side contains something you can't assign to, leading to the mistake.
How to gear up this error: Brand certain you're not attempting to assign values to role results or to the this keyword.
Uncaught TypeError: Converting round construction to JSON
Related errors: Uncaught exception: TypeError: JSON.stringify: Not an acyclic Object, TypeError: cyclic object value, Circular reference in value statement not supported
Always acquired past a circular reference in an object, which is and so passed into JSON.stringify.
var a = { }; var b = { a: a }; a.b = b; JSON.stringify(a); Because both a and b in the above case have a reference to each other, the resulting object cannot be converted into JSON.
How to fix this mistake: Remove circular references like in the example from any objects yous want to catechumen into JSON.
Unexpected token ;
Related errors: Expected ), missing ) afterwards argument listing
The JavaScript interpreter expected something, but it wasn't in that location. Typically acquired by mismatched parentheses or brackets.
The token in this error can vary – it might say "Unexpected token ]" or "Expected {" etc.
How to fix this error: Sometimes the line number with this fault doesn't point to the correct identify, making it difficult to ready.
- An error with [ ] { } ( ) is unremarkably acquired by a mismatching pair. Check that all your parentheses and brackets have a matching pair. In this case, line number volition often point to something else than the problem graphic symbol
- Unexpected / is related to regular expressions. The line number for this will usually be correct.
- Unexpected ; is unremarkably caused by having a ; inside an object or array literal, or inside the argument list of a role telephone call. The line number will usually exist correct for this case besides
Uncaught SyntaxError: Unexpected token ILLEGAL
Related errors: Unterminated String Literal, Invalid Line Terminator
A string literal is missing the closing quote.
How to gear up this error: Ensure all strings have the correct closing quote.
Uncaught TypeError: Cannot read belongings 'foo' of null, Uncaught TypeError: Cannot read property 'foo' of undefined
Related errors: TypeError: someVal is nix, Unable to become belongings 'foo' of undefined or zippo reference
Attempting to read null or undefined as if information technology was an object. For case:
var someVal = null; panel.log(someVal.foo);
How to fix this error: Normally acquired past typos. Cheque that the variables used virtually the line number pointed past the error are correctly named.
Uncaught TypeError: Cannot set property 'foo' of zero, Uncaught TypeError: Cannot set property 'foo' of undefined
Related errors: TypeError: someVal is undefined, Unable to gear up property 'foo' of undefined or null reference
Attempting to write null or undefined as if it was an object. For example:
var someVal = zip; someVal.foo = one;
How to fix this mistake: This too is unremarkably caused past typos. Check the variable names near the line the mistake points to.
Uncaught RangeError: Maximum telephone call stack size exceeded
Related errors: Uncaught exception: RangeError: Maximum recursion depth exceeded, too much recursion, Stack overflow
Usually caused by a bug in program logic, causing infinite recursive office calls.
How to fix this error: Bank check recursive functions for bugs that could cause them to keep recursing forever.
Uncaught URIError: URI malformed
Related errors: URIError: malformed URI sequence
Caused by an invalid decodeURIComponent call.
How to fix this error: Check that the decodeURIComponent call at the error'due south line number gets correct input.
XMLHttpRequest cannot load http://some/url/. No 'Access-Control-Allow-Origin' header is present on the requested resources
Related errors: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://some/url/
This error is e'er caused by the usage of XMLHttpRequest.
How to fix this mistake: Ensure the request URL is right and it respects the aforementioned-origin policy. A good style to find the offending code is to look at the URL in the fault message and discover information technology from your code.
InvalidStateError: An endeavor was made to use an object that is non, or is no longer, usable
Related errors: InvalidStateError, DOMException code 11
Ways the code chosen a function that you should not call at the current state. Occurs normally with XMLHttpRequest, when attempting to call functions on it before information technology's ready.
var xhr = new XMLHttpRequest(); xhr.setRequestHeader('Some-Header', 'val'); In this case, yous would get the mistake considering the setRequestHeader function tin can but exist called after calling xhr.open.
How to fix this error: Await at the lawmaking on the line pointed by the error and brand certain it runs at the correct time, or add whatever necessary calls before it (such equally xhr.open)
Conclusion
JavaScript has some of the most unhelpful errors I've seen, with the exception of the notorious Expected T_PAAMAYIM_NEKUDOTAYIM in PHP. With more familiarity the errors first to make more sense. Modern browsers also aid, equally they no longer give the completely useless errors they used to.
What'south the most confusing error yous've seen? Share the frustration in the comments!
Want to learn more than nigh these errors and how to prevent them? Detect Problems in JavaScript Automatically with ESLint.
About Jani Hartikainen
Jani Hartikainen has spent over 10 years building spider web applications. His clients include companies like Nokia and hot super secret startups. When not programming or playing games, Jani writes most JavaScript and high quality code on his site.
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Source: https://davidwalsh.name/fix-javascript-errors
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