linux - eval and export remove the double quote (") from the string

I want to export a string with eval in the following way. But I get the string without quotes as indication in the following example

root@linux:~# a="{\"name\":\"any\"}"
root@linux:~# echo $a
{"name":"any"}

root@linux:~# eval "export -- \"b=\"\"$a\"\"\""
root@linux:~# echo $b
{name:any} ------>> expect {"name":"any"}

How to solve this problem?

Answer

I'm going to set aside that I don't quite understand why you are doing it like this, but try the following:

bash-3.2$ a="{\"name\":\"any\"}"

bash-3.2$ echo $a
{"name":"any"}
bash-3.2$ eval "export -- b='$a'"
bash-3.2$ echo $b
{"name":"any"}
bash-3.2$