Aws Signer Typeerror: Cannot Read Property 'split' of Undefined

JavaScript Errors and How to Ready Them

JavaScript tin exist a nightmare to debug: Some errors it gives can be very hard to empathize at offset, and the line numbers given aren't always helpful either. Wouldn't it be useful to accept a list where you lot could await to find out what they mean and how to fix them? Here you lot go!

Below is a list of the strange errors in JavaScript. Unlike browsers can give you different messages for the same error, then there are several different examples where applicable.

How to read errors?

Before the list, let's apace wait at the construction of an mistake bulletin. Understanding the structure helps understand the errors, and yous'll have less problem if you run into whatever errors not listed here.

A typical error from Chrome looks like this:

Uncaught TypeError: undefined is not a office

The structure of the mistake is as follows:

1. Uncaught TypeError: This part of the bulletin is commonly not very useful. Uncaught ways the error was not caught in a catch statement, and TypeError is the error'due south name.
2. undefined is not a function: This is the message part. With error letters, yous have to read them very literally. For example in this case information technology literally ways that the code attempted to use undefined like it was a function.

Other webkit-based browsers, similar Safari, give errors in a like format to Chrome. Errors from Firefox are similar, but do not always include the first function, and recent versions of Internet Explorer also give simpler errors than Chrome – but in this example, simpler does non always hateful amend.

Now onto the actual errors.

Uncaught TypeError: undefined is not a office

Related errors: number is not a role, object is non a function, string is not a function, Unhandled Mistake: 'foo' is not a function, Function Expected

Occurs when attempting to telephone call a value like a role, where the value is not a function. For case:

var foo = undefined; foo();

This mistake typically occurs if you are trying to call a function in an object, but you typed the name incorrect.

var x = certificate.getElementByID('foo');

Since object properties that don't be are undefined by default, the to a higher place would result in this error.

The other variations such as "number is non a function" occur when attempting to call a number like it was a function.

How to set this error: Ensure the role name is correct. With this mistake, the line number will ordinarily bespeak at the correct location.

Uncaught ReferenceError: Invalid left-manus 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 exist assigned to.

The most common instance of this error is with if-clauses:

if(doSomething() = 'somevalue')

In this example, the programmer accidentally used a unmarried equals instead of two. The message "left-hand side in consignment" is referring to the part on the left side of the equals sign, so similar you can see in the above example, the left-hand side contains something you can't assign to, leading to the mistake.

How to fix this error: Brand certain you're not attempting to assign values to function results or to the this keyword.

Uncaught TypeError: Converting circular construction to JSON

Related errors: Uncaught exception: TypeError: JSON.stringify: Non an acyclic Object, TypeError: cyclic object value, Circular reference in value argument not supported

E'er acquired past a circular reference in an object, which is then 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 error: Remove round references like in the example from any objects you desire to convert into JSON.

Unexpected token ;

Related errors: Expected ), missing ) after argument list

The JavaScript interpreter expected something, just information technology wasn't there. Typically caused past mismatched parentheses or brackets.

The token in this error can vary – information technology might say "Unexpected token ]" or "Expected {" etc.

How to ready this error: Sometimes the line number with this fault doesn't signal to the right identify, making it hard to fix.

• An error with [ ] { } ( ) is ordinarily acquired by a mismatching pair. Bank check that all your parentheses and brackets have a matching pair. In this case, line number volition oftentimes betoken to something else than the problem character
• Unexpected / is related to regular expressions. The line number for this will usually exist correct.
• Unexpected ; is normally caused by having a ; inside an object or assortment literal, or within the argument list of a part call. The line number will usually be correct for this case besides

Uncaught SyntaxError: Unexpected token ILLEGAL

Related errors: Unterminated String Literal, Invalid Line Terminator

A cord literal is missing the closing quote.

How to fix this error: Ensure all strings have the correct closing quote.

Uncaught TypeError: Cannot read property 'foo' of nothing, Uncaught TypeError: Cannot read property 'foo' of undefined

Related errors: TypeError: someVal is nix, Unable to get holding 'foo' of undefined or nix reference

Attempting to read goose egg or undefined as if it was an object. For instance:

var someVal = nothing; console.log(someVal.foo);

How to fix this error: Usually caused by typos. Check that the variables used well-nigh the line number pointed by the error are correctly named.

Uncaught TypeError: Cannot set property 'foo' of null, Uncaught TypeError: Cannot set belongings 'foo' of undefined

Related errors: TypeError: someVal is undefined, Unable to gear up holding 'foo' of undefined or null reference

Attempting to write null or undefined equally if it was an object. For example:

var someVal = null; someVal.foo = 1;

How to prepare this error: This too is commonly acquired by typos. Check the variable names near the line the error points to.

Uncaught RangeError: Maximum call stack size exceeded

Related errors: Uncaught exception: RangeError: Maximum recursion depth exceeded, too much recursion, Stack overflow

Unremarkably caused by a bug in program logic, causing infinite recursive role calls.

How to fix this fault: Cheque 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 fault: Check that the decodeURIComponent call at the mistake'due south line number gets right input.

XMLHttpRequest cannot load http://some/url/. No 'Access-Command-Let-Origin' header is nowadays on the requested resource

Related errors: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resources at http://some/url/

This error is always caused by the usage of XMLHttpRequest.

How to fix this fault: Ensure the request URL is correct and information technology respects the same-origin policy. A good style to find the offending lawmaking is to look at the URL in the error message and find it from your lawmaking.

InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable

Related errors: InvalidStateError, DOMException code eleven

Ways the lawmaking chosen a role that yous should not phone call at the current country. Occurs normally with XMLHttpRequest, when attempting to call functions on it earlier it's ready.

var xhr = new XMLHttpRequest(); xhr.setRequestHeader('Some-Header', 'val');

In this instance, you would get the fault because the setRequestHeader function tin but be called after calling xhr.open.

How to fix this fault: Look at the code on the line pointed by the error and make sure it runs at the right time, or add whatever necessary calls before it (such as xhr.open up)

Determination

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 start to make more sense. Modernistic browsers also help, every bit they no longer give the completely useless errors they used to.

What's the most confusing fault you lot've seen? Share the frustration in the comments!

Want to larn more about these errors and how to prevent them? Detect Problems in JavaScript Automatically with ESLint.

Well-nigh Jani Hartikainen

Jani Hartikainen has spent over 10 years building web applications. His clients include companies like Nokia and hot super hugger-mugger startups. When not programming or playing games, Jani writes well-nigh JavaScript and high quality code on his site.

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Source: https://davidwalsh.name/fix-javascript-errors

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