An issue arises when using JSON.parse() with regular expression values

Question

An issue arises when using JSON.parse() with regular expression values

I am encountering an issue with parsing a JSON string encoded with PHP 5.2 json_encode(). Here is the JSON string:

{"foo":"\\."}

Although this JSON string is valid according to jsonlint.com, when using the native JSON.parse() method in Chrome and Firefox, I receive the following error:

SyntaxError: Unexpected token ILLEGAL

I would like to know why escaped regular expression meta characters cannot be parsed. For instance, this example works:

{"foo":"\\bar"}

But this one fails:

{"foo":"\\?"}

For clarification, \. is just a simple test regular expression that I want to execute using JavaScript's RegExp object.

Your assistance is greatly appreciated.

Regards,
Dyvor

javascript regex json firefox google-chrome

Answer 1

Answer №1

The reason it's not functioning correctly is due to a crucial factor you might be overlooking: there are actually two string parsing processes occurring when you enter a line like this into the Chrome console:

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

The initial string parsing occurs when the JavaScript interpreter interprets the string constant being passed into the "parse()" method. The second string parsing takes place within the JSON parser itself. After the first pass, the double backslash becomes just a single backslash.

On the other hand, this example:

{"foo":"\\bar"}

successfully works because "\b" represents a valid intra-string escape sequence.

Answer 2

The reason it's not functioning correctly is due to a crucial factor you might be overlooking: there are actually two string parsing processes occurring when you enter a line like this into the Chrome console:

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

The initial string parsing occurs when the JavaScript interpreter interprets the string constant being passed into the "parse()" method. The second string parsing takes place within the JSON parser itself. After the first pass, the double backslash becomes just a single backslash.

On the other hand, this example:

{"foo":"\\bar"}

successfully works because "\b" represents a valid intra-string escape sequence.

Answer 3

Answer №2

This solution worked successfully for me when using the firebug console.

>>> JSON.parse('"\\\\."');
"\."

The JSON parser correctly interprets "\\." as escaped backslashes and a dot.

Have you experienced this issue with PHP responses, or only during manual testing?

Answer 4

This solution worked successfully for me when using the firebug console.

>>> JSON.parse('"\\\\."');
"\."

The JSON parser correctly interprets "\\." as escaped backslashes and a dot.

Have you experienced this issue with PHP responses, or only during manual testing?

Answer 5

Answer №3

Include an additional pair of \\, the reason behind its functionality remains somewhat mysterious to me.

JSON.parse('{"bar":"\\\\\\."}');

Answer 6

Include an additional pair of \\, the reason behind its functionality remains somewhat mysterious to me.

JSON.parse('{"bar":"\\\\\\."}');

An issue arises when using JSON.parse() with regular expression values

Answer №1

Answer №2

Answer №3

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