Json parse array error

SyntaxError: JSON.parse: bad parsing

Deeksha Agarwal

Posted On: April 5, 2018

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JSON or JavaScript Object Notation is a ubiquitous data format used by all sorts of mobile and web apps for asynchronous browser-server communication. JSON is an extremely popular data format, very easy to work with, compatible with every major programming language, and is supported by every major browser. However just like any programming language, it throws a lot of errors when it decide that today is not going to be your day.

JSON.Parse Syntax Errors

In most web applications, nearly all data transferred from web server is transmitted in a string format. To convert that string into JSON, we use JSON.parse() function, and this the main function that throws errors. Nearly all JSON.parse errors are a subset of SyntaxError error type. Debugging console throws around 32 different errors messages when you mess up your JSON data. And some of them are very tricky to debug; and yes I am talking about you unexpected non-whitespace character after JSON data .

Why the SyntaxError Horror?

SyntaxError is an inherited object of the main error object The main reason behind the error is usually a mistake in the JSON file syntax. You mess up and put a “ instead of a ‘ and you invite to face the SyntaxError JSON.parse: unexpected character .

Just like every programming language, a JSON file has a fixed syntax. Small syntax errors throws errors. For example, in the following code, i forgot to remove a trailing comma

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Exceptions¶

Overview¶

Base type¶

All exceptions inherit from class json::exception (which in turn inherits from std::exception ). It is used as the base class for all exceptions thrown by the basic_json class. This class can hence be used as «wildcard» to catch exceptions.

Switch off exceptions¶

Exceptions are used widely within the library. They can, however, be switched off with either using the compiler flag -fno-exceptions or by defining the symbol JSON_NOEXCEPTION . In this case, exceptions are replaced by abort() calls. You can further control this behavior by defining JSON_THROW_USER (overriding throw ), JSON_TRY_USER (overriding try ), and JSON_CATCH_USER (overriding catch ).

Note that JSON_THROW_USER should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.

The code below switches off exceptions and creates a log entry with a detailed error message in case of errors.

Note the explanatory what() string of exceptions is not available for MSVC if exceptions are disabled, see #2824.

Extended diagnostic messages¶

Exceptions in the library are thrown in the local context of the JSON value they are detected. This makes detailed diagnostics messages, and hence debugging, difficult.

This exception can be hard to debug if storing the value «12» and accessing it is further apart.

To create better diagnostics messages, each JSON value needs a pointer to its parent value such that a global context (i.e., a path from the root value to the value that lead to the exception) can be created. That global context is provided as JSON Pointer.

As this global context comes at the price of storing one additional pointer per JSON value and runtime overhead to maintain the parent relation, extended diagnostics are disabled by default. They can, however, be enabled by defining the preprocessor symbol JSON_DIAGNOSTICS to 1 before including json.hpp .

Now the exception message contains a JSON Pointer /address/housenumber that indicates which value has the wrong type.

Parse errors¶

This exception is thrown by the library when a parse error occurs. Parse errors can occur during the deserialization of JSON text, CBOR, MessagePack, as well as when using JSON Patch.

Exceptions have ids 1xx.

Member byte holds the byte index of the last read character in the input file.

For an input with n bytes, 1 is the index of the first character and n+1 is the index of the terminating null byte or the end of file. This also holds true when reading a byte vector (CBOR or MessagePack).

The following code shows how a parse_error exception can be caught.

json.exception.parse_error.101¶

This error indicates a syntax error while deserializing a JSON text. The error message describes that an unexpected token (character) was encountered, and the member byte indicates the error position.

Input ended prematurely:

Control character was not escaped:

String was not closed:

Invalid number format:

u was not be followed by four hex digits:

Invalid UTF-8 surrogate pair:

Invalid UTF-8 byte:

• Make sure the input is correctly read. Try to write the input to standard output to check if, for instance, the input file was successfully opened.
• Paste the input to a JSON validator like http://jsonlint.com or a tool like jq.

json.exception.parse_error.102¶

JSON uses the uxxxx format to describe Unicode characters. Code points above 0xFFFF are split into two uxxxx entries («surrogate pairs»). This error indicates that the surrogate pair is incomplete or contains an invalid code point.

This exception is not used any more. Instead json.exception.parse_error.101 with a more detailed description is used.

json.exception.parse_error.103¶

Unicode supports code points up to 0x10FFFF. Code points above 0x10FFFF are invalid.

This exception is not used any more. Instead json.exception.parse_error.101 with a more detailed description is used.

json.exception.parse_error.104¶

RFC 6902 requires a JSON Patch document to be a JSON document that represents an array of objects.

json.exception.parse_error.105¶

An operation of a JSON Patch document must contain exactly one «op» member, whose value indicates the operation to perform. Its value must be one of «add», «remove», «replace», «move», «copy», or «test»; other values are errors.

json.exception.parse_error.106¶

An array index in a JSON Pointer (RFC 6901) may be 0 or any number without a leading 0 .

json.exception.parse_error.107¶

A JSON Pointer must be a Unicode string containing a sequence of zero or more reference tokens, each prefixed by a / character.

json.exception.parse_error.108¶

In a JSON Pointer, only

1 are valid escape sequences.

json.exception.parse_error.109¶

A JSON Pointer array index must be a number.

json.exception.parse_error.110¶

When parsing CBOR or MessagePack, the byte vector ends before the complete value has been read.

json.exception.parse_error.112¶

An unexpected byte was read in a binary format or length information is invalid (BSON).

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How to Fix the ‘SyntaxError: JSON.parse: bad parsing ‘ Error in Our JavaScript App?

By John Au-Yeung
Post date

Sometimes, we may run into the ‘SyntaxError: JSON.parse: bad parsing’ when we’re developing JavaScript apps.

In this article, we’ll look at how to fix the ‘SyntaxError: JSON.parse: bad parsing’ when we’re developing JavaScript apps.

Fix the ‘SyntaxError: JSON.parse: bad parsing’ When Developing JavaScript Apps

To fix the ‘SyntaxError: JSON.parse: bad parsing’ when we’re developing JavaScript apps, we should make sure we pass in a valid JSON string as an argument of the JSON.parse method.

Other possible error messages for various JSON parse errors include:

For instance, we shouldn’t pass in a JSON string that has trailing commas:

The first line has a trailing comma at the end of the array.

The 2nd has a trailing commas at the end of the object.

Instead, we should fix the error by removing them:

Also, property names must be double quoted strings, so instead of writing:

Also, we can’t have numbers with leading zeroes in our JSON string:

Instead, we fix that by removing the leading zero:

Trailing decimal points are also invalid JSON, so we can’t write:

Instead, we write:

Conclusion

To fix the ‘SyntaxError: JSON.parse: bad parsing’ when we’re developing JavaScript apps, we should make sure we pass in a valid JSON string as an argument of the JSON.parse method.

To check if a string is JSON in JavaScript, we can use the JSON.parse method…

Sometimes, we may run into the “unexpected token o” error when parsing JSON in our…

Sometimes, we want to convert a JSON string into a JavaScript object. In this article,…

By John Au-Yeung

Web developer specializing in React, Vue, and front end development.

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SyntaxError: JSON.parse: bad parsing

Tired of getting this annoying error when your parsing your JSON? Read on to learn how!

Join the DZone community and get the full member experience.

JSON, or JavaScript Object Notation, is a ubiquitous data format used by all sorts of mobile and web apps for asynchronous browser-server communication. JSON is an extremely popular data format, very easy to work with, compatible with every major programming language, and is supported by every major browser. However, just like any programming language, it throws a lot of errors when it decides that today is not going to be your day.

JSON.Parse Syntax Errors

In most web applications, nearly all data transferred from a web server is transmitted in a string format. To convert that string into JSON, we use the JSON.parse() function, and this is the main function that throws errors. Nearly all JSON.parse errors are a subset of the SyntaxError error type. The debugging console throws around 32 different error messages when you mess up your JSON data. And some of them are very tricky to debug; and yes I am talking about you unexpected non-whitespace character after JSON data .

Why the SyntaxError Horror?

SyntaxError is an inherited object of the main error object The main reason behind the error is usually a mistake in the JSON file syntax. You mess up and put a “ instead of a ‘ and you invite to face the SyntaxError JSON.parse: unexpected character .

Just like every programming language, a JSON file has a fixed syntax. Small syntax errors throws errors. For example, in the following code, I forgot to remove a trailing comma

Similarly, in this example, I forgot to add the final > character.

How to Catch the Error Before Hand

The problem with debugging JSON errors is that you only get to know about one error at a time. Debuggers throw the first error they find and then stop. It would be up to you to regression find the bugs. Usually, it’s not as difficult as it sounds.

The first step is to make sure that your JSON file is perfect from the get go. Here you can take help from JSON linting tools like cleverly named jsonlint.com

If you don’t have any control over the receiving JSON file, then the next step is to add catch exceptions around your JSON.parse.

Also, here are the main errors related to JSON.parse that I very painstakingly collected from a very single source [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/JSON_bad_parse]:

If this doesn’t help, then you are in for one long debugging session.

Published at DZone with permission of Deeksha Agarwal . See the original article here.

Opinions expressed by DZone contributors are their own.

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Traveling deftly through to the next item in our JavaScript Error Handling series, today we’re taking a hard look at the JSON Parse error. The JSON Parse error, as the name implies, surfaces when using the JSON.parse() method that fails to pass valid JSON as an argument.

In this article, we’ll dig deeper into where JSON Parse errors sit in the JavaScript error hierarchy, as well as when it might appear and how to handle it when it does. Let’s get started!

The Technical Rundown

• All JavaScript error objects are descendants of the Error object, or an inherited object therein.
• The SyntaxError object is inherited from the Error object.
• The JSON Parse error is a specific type of SyntaxError object.

When Should You Use It?

While most developers are probably intimately familiar with JSON and the proper formatting syntax it requires, it doesn’t hurt to briefly review it ourselves, to better understand some common causes of the JSON Parse error in JavaScript.

JavaScript Object Notation, better known as JSON, is a human-readable text format, commonly used to transfer data across the web. The basic structure of JSON consists of objects, which are sets of string: value pairs surrounded by curly braces:

{

    "first": "Jane",

    "last": "Doe"

}

An array is a set of values, surrounded by brackets:

[

    "Jane",

    "Doe"

]

A value can be a string, number, object, array, boolean, or null.

That’s really all there is to the JSON syntax. Since values can be other objects or arrays, JSON can be infinitely nested (theoretically).

In JavaScript, when passing JSON to the JSON.parse() method, the method expects properly formatted JSON as the first argument. When it detects invalid JSON, it throws a JSON Parse error.

For example, one of the most common typos or syntax errors in JSON is adding an extra comma separator at the end of an array or object value set. Notice in the first few examples above, we only use a comma to literally separate values from one another. Here we’ll try adding an extra, or «hanging», comma after our final value:

var printError = function(error, explicit) {

    console.log(`[${explicit ? 'EXPLICIT' : 'INEXPLICIT'}] ${error.name}: ${error.message}`);

}

try {
var json = `
{
«first»: «Jane»,
«last»: «Doe»,
}
`
console.log(JSON.parse(json));
} catch (e) {
if (e instanceof SyntaxError) {
printError(e, true);
} else {
printError(e, false);
}
}

Note: We’re using the backtick (`) string syntax to initialize our JSON, which just allows us to present it in a more readable form. Functionally, this is identical to a string that is contained on a single line.

As expected, our extraneous comma at the end throws a JSON Parse error:

[EXPLICIT] SyntaxError: Unexpected token } in JSON at position 107

In this case, it’s telling us the } token is unexpected, because the comma at the end informs JSON that there should be a third value to follow.

Another common syntax issue is neglecting to surround string values within string: value pairs with quotations ("). Many other language syntaxes use similar key: value pairings to indicate named arguments and the like, so developers may find it easy to forget that JSON requires the string to be explicitly indicated using quotation marks:

var printError = function(error, explicit) {

    console.log(`[${explicit ? 'EXPLICIT' : 'INEXPLICIT'}] ${error.name}: ${error.message}`);

}

try {
var json = `
{
«first»: «Jane»,
last: «Doe»,
}
`
console.log(JSON.parse(json));
} catch (e) {
if (e instanceof SyntaxError) {
printError(e, true);
} else {
printError(e, false);
}
}

Here we forgot quotations around the "last" key string, so we get another JSON Parse error:

[EXPLICIT] SyntaxError: Unexpected token l in JSON at position 76

A few examples are probably sufficient to see how the JSON Parse error comes about, but as it so happens, there are dozens of possible versions of this error, depending on how JSON was improperly formatted. Here’s the full list:

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An Easier Way to Find JavaScript Errors

The first way to find a JSON Parse error is to go through your logs, but when you’re dealing with hundreds, if not thousands, of lines of code, it can be difficult to find that one line of broken code. With Airbrake Error and Performance Monitoring, you can skip the logs and go straight to the line of broken code resulting in the JSON Parse error.

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JSON ( JavaScript Object Notation), is widely used format for asynchronous communication between webpage or mobile application to back-end servers. Due to increasing trend in Single Page Application or Mobile Application, popularity of the JSON is extreme.

Why do we get JSON parse error?

Parsing JSON is a very common task in JavaScript. JSON.parse() is a built-in method in JavaScript which is used to parse a JSON string and convert it into a JavaScript object. If the JSON string is invalid, it will throw a SyntaxError.

const json = '{"result":true, "count":42}';
const obj = JSON.parse(json);
console.log(obj.count);
// expected output: 42
console.log(obj.result);
// expected output: true

How to handle JSON parse error?

There are many ways to handle JSON parse error. In this post, I will show you how to handle JSON parse error in JavaScript.

1. Using try-catch block

The most common way to handle JSON parse error is using try-catch block. If the JSON string is valid, it will return a JavaScript object. If the JSON string is invalid, it will throw a SyntaxError.

try {
  const json = '{"result":true, "count":42}';
  const obj = JSON.parse(json);
  console.log(obj.count);
  // expected output: 42
  console.log(obj.result);
  // expected output: true
} catch (e) {
  console.log(e);
  // expected output: SyntaxError: Unexpected token o in JSON at position 1
}

2. Using if-else block

Another way to handle JSON parse error is using if-else block.

const json = '{"result":true, "count":42}';
const obj = JSON.parse(json);
if (obj instanceof SyntaxError) {
  console.log(obj);
  // expected output: SyntaxError: Unexpected token o in JSON at position 1
} else {
  console.log(obj.count);
  // expected output: 42
  console.log(obj.result);
  // expected output: true
}

3. Using try-catch block with JSON.parse()

The third way to handle JSON parse error is using try-catch block with JSON.parse().

const json = '{"result":true, "count":42}';
const obj = JSON.parse(json, (key, value) => {
  try {
    return JSON.parse(value);
  } catch (e) {
    return value;
  }
});
console.log(obj.count);
// expected output: 42
console.log(obj.result);
// expected output: true

4. Using try-catch block with JSON.parse() and JSON.stringify()

The fourth way to handle JSON parse error is using try-catch block with JSON.parse() and JSON.stringify(). If the JSON string is valid, it will return a JavaScript object. If the JSON string is invalid, it will return a SyntaxError.

const json = '{"result":true, "count":42}';
const obj = JSON.parse(json, (key, value) => {
  try {
    return JSON.parse(value);
  } catch (e) {
    return value;
  }
});
const str = JSON.stringify(obj);
console.log(str);
// expected output: {"result":true,"count":42}