Common JSON Errors

JavaScript Object Notation (JSON) is one of the most popular data formats used in web development. It's a lightweight, text-based format that makes it easy to store and share data across applications. However, like any technology, there are some common errors that web developers need to be aware of when working with JSON. Let's take a look at a few of these errors.

Syntax Errors

One of the most common types of errors encountered when working with JSON is syntax errors. These occur when you make mistakes such as forgetting a comma between two items or using an invalid character in your JSON string.

Syntax errors can also occur if you forget to close a quotation mark or accidentally type two instead of one.

Many developers tend to use a single quote to wrap a string. This will cause an error on a JSON string. You must use a double quote for string.

To fix these errors, simply double-check your code for any typos or missed characters and make sure that all quotations are closed properly.

Here is an example of JSON code with a missing comma:

{
  "name": "Robert Johnson",
  "age": 52 //missing comma here
  "email": "[email protected]"
}

In this code, the comma is missing after the "age": 52 line, which is a syntax error. JSON requires that every key-value pair except for the last one in an object must be followed by a comma. This code would need to be corrected by adding a comma after the "age": 52 line, like this:

{
  "name": "Robert Johnson",
  "age": 52,
  "email": "[email protected]"
}

Data Type Mismatches

Data type mismatch happens when you try to assign a value to an incorrect data type—such as assigning a number to a string field—or if you try to use the wrong syntax for an object or array.

To avoid this mistake, always double-check that the data types in your code match up and that you're using the correct syntax for objects and arrays.

Wrong:

{
  "name": "Maria Garcia",
  "age": "36",
  "email": "[email protected]",
  "is_admin": "false"
}

Correct:

{
  "name": "Maria Garcia",
  "age": 36,
  "email": "[email protected]",
  "is_admin": false
}

Incorrectly Escaped Characters

Another mistake that can occur with JSON is incorrectly escaped characters, which are special symbols used in programming languages like JavaScript and HTML to represent certain characters such as quotation marks and apostrophes. This is because these special characters have special meanings in JSON, and if they are not escaped properly, they can cause syntax errors.

If these characters aren't correctly escaped in your code, they won't be interpreted properly by the browser or application trying to read them. To avoid this issue, always use the appropriate escape sequence for each character in your code.

Certain special characters, such as double quotes, must be escaped with a backslash in order to be used as part of a string value.

Wrong:

{
  "name": "John Doe",
  "favorite_quote": "YOLO is an acronym that stands for "You Only Live Once.""
}

Correct:

{
  "name": "John Doe",
  "favorite_quote": "YOLO is an acronym that stands for \"You Only Live Once.\""
}

Mixing Up the Order of Keys and Values

Another common error is mixing up the order of keys and values in JSON objects. In JSON, keys and values must be separated by a colon, with the key on the left side and the value on the right side. Mixing up the order can result in invalid JSON and cause errors when the JSON is parsed.

Here is an example of JSON code with a mixing up the order of keys and values error:

Wrong:

{
  "name": "John Doe",
  "[email protected]": "email",
  "false": "is_admin"
}

In this code, the age, email, and is_admin fields have their keys and values mixed up. This is a syntax error because in JSON, keys must always be strings, and values can be any valid JSON data type (such as strings, numbers, booleans, etc.). To correct this error, the keys and values for the age, email, and is_admin fields should be switched, like this:

Correct:

{
  "name": "John Doe",
  "email": "[email protected]",
  "is_admin": false
}
In JSON, keys and values must be arranged in a specific order: keys must be strings, and values must follow the corresponding keys. Mixing up the order of keys and values is a syntax error that can cause issues when parsing and interpreting the JSON data.