SyntaxError: JSON.parse: bad parsing

The error message is as follows.

SyntaxError: JSON.parse: bad parsing

Console Tip.

SyntaxError: JSON.parse: unterminated string literal
SyntaxError: JSON.parse: bad control character in string literal
SyntaxError: JSON.parse: bad character in string literal
SyntaxError: JSON.parse: bad Unicode escape
SyntaxError: JSON.parse: bad escape character
SyntaxError: JSON.parse: unterminated string
SyntaxError: JSON.parse: no number after minus sign
SyntaxError: JSON.parse: unexpected non-digit
SyntaxError: JSON.parse: missing digits after decimal point
SyntaxError: JSON.parse: unterminated fractional number
SyntaxError: JSON.parse: missing digits after exponent indicator
SyntaxError: JSON.parse: missing digits after exponent sign
SyntaxError: JSON.parse: exponent part is missing a number
SyntaxError: JSON.parse: unexpected end of data
SyntaxError: JSON.parse: unexpected keyword
SyntaxError: JSON.parse: unexpected character
SyntaxError: JSON.parse: end of data while reading object contents
SyntaxError: JSON.parse: expected property name or '}'
SyntaxError: JSON.parse: end of data when ',' or ']' was expected
SyntaxError: JSON.parse: expected ',' or ']' after array element
SyntaxError: JSON.parse: end of data when property name was expected
SyntaxError: JSON.parse: expected double-quoted property name
SyntaxError: JSON.parse: end of data after property name when ':' was expected
SyntaxError: JSON.parse: expected ':' after property name in object
SyntaxError: JSON.parse: end of data after property value in object
SyntaxError: JSON.parse: expected ',' or '}' after property value in object
SyntaxError: JSON.parse: expected ',' or '}' after property-value pair in object literal
SyntaxError: JSON.parse: property names must be double-quoted strings
SyntaxError: JSON.parse: expected property name or '}'
SyntaxError: JSON.parse: unexpected character
SyntaxError: JSON.parse: unexpected non-whitespace character after JSON data

What went wrong?

JSON.parse() will parse a string into a JSON object. If the string is written correctly, it will be parsed into a valid JSON, but the string will throw an error if an incorrect syntax is detected.

Example

JSON.parse() does not allow extra commas at the end

The following two lines of code both throw errors.

JSON.parse('[1, 2, 3, 4, ]');
JSON.parse('{"foo" : 1, }');
// SyntaxError JSON.parse: unexpected character
// at line 1 column 14 of the JSON data

Omitting the extra comma at the end of the parsed JSON is the correct.

JSON.parse('[1, 2, 3, 4 ]');
JSON.parse('{"foo" : 1 }');

JSON attribute names must be enclosed in double quotes

Single quotes cannot be used on attribute names, e.g., ‘foo’.

JSON.parse("{'foo' : 1 }");
// SyntaxError: JSON.parse: expected property name or '}'
// at line 1 column 2 of the JSON data

Instead, write “foo” as follows.

JSON.parse('{"foo" : 1 }');

Leading 0 and decimal point

The number cannot start with a 0, such as 01, and your decimal point must be followed by at least one digit.

JSON.parse('{"foo" : 01 }');
// SyntaxError: JSON.parse: expected ',' or '}' after property value
// in object at line 1 column 2 of the JSON data

JSON.parse('{"foo" : 1. }');
// SyntaxError: JSON.parse: unterminated fractional number
// at line 1 column 2 of the JSON data

The correct way to write a 1 is to write only a 1, without the leading 0. Follow the decimal point with at least one digit.

JSON.parse('{"foo" : 1 }');
JSON.parse('{"foo" : 1.0 }');