Regular expression to extract a JSON array - json

Question

I'm trying to use a PCRE regular expression to extract some JSON. I'm using a version of MariaDB which does not have JSON functions but does have REGEX functions.
My string is:
{"device_types":["smartphone"],"isps":["a","B"],"network_types":[],"countries":[],"category":["Jebb","Bush"],"carriers":[],"exclude_carriers":[]}
I want to grab the contents of category. I'd like a matching group that contains 2 items, Jebb and Bush (or however many items are in the array).
I've tried this pattern but it only matches the first occurrence: /(?<=category":\[).([^"]*).*?(?=\])/g

Answer 1

Does this match your needs? It should match the category array regardless of its size.
"category":(\[.*?\])
regex101 example

Answer 2

JSON not a regular language. Since it allows arbitrary embedding of balanced delimiters, it must be at least context-free.
For example, consider an array of arrays of arrays:
[ [ [ 1, 2], [2, 3] ] , [ [ 3, 4], [ 4, 5] ] ]
Clearly you couldn't parse that with true regular expressions.
See This Topic:
Regex for parsing single key: values out of JSON in Javascript
Maybe Helpful for you.

Answer 3

Using a set of non-capturing group you can extract a predefined json array
regex answer: (?:\"category\":)(?:\[)(.*)(?:\"\])
That expression extract "category":["Jebb","Bush"], so access the first group
to extract the array, sample java code:
Pattern pattern = Pattern.compile("(?:\"category\":)(?:\\[)(.*)(?:\"\\])");
String body = "{\"device_types\":[\"smartphone\"],\"isps\":[\"a\",\"B\"],\"network_types\":[],\"countries\":[],\"category\":[\"Jebb\",\"Bush\"],\"carriers\":[],\"exclude_carriers\":[]}";
Matcher matcher = pattern.matcher(body);
assertThat(matcher.find(), is(true));
String[] categories = matcher.group(1).replaceAll("\"","").split(",");
assertThat(categories.length, is(2));
assertThat(categories[0], is("Jebb"));
assertThat(categories[1], is("Bush"));

Answer 4

There are many ways. One sloppy way to do it is /([A-Z])\w+/g
Please try it on your console like
var data = '{"device_types":["smartphone"],"isps":["a","B"],"network_types":[],"countries":[],"category":["Jebb","Bush"],"carriers":[],"exclude_carriers":[]}',
res = [];
data.match(/([A-Z])\w+/g); // ["Jebb", "Bush"]
OK the above was pretty sloppy however a solid single regex solution to extract every single element regardless of the number, one by one and to place them in an array (res) is the following...
var rex = /[",]+(\w*)(?=[",\w]*"],"carriers)/g,
str = '{"device_types":["smartphone"],"isps":["a","B"],"network_types":[],"countries":[],"category":["Jebb","Bush","Donald","Trump"],"carriers":[],"exclude_carriers":[]}',
arr = [],
res = [];
while ((arr = rex.exec(str)) !== null) {
res.push(arr[1]); // <- ["Jebb", "Bush", "Donald", "Trump"]
}
Check it out # http://regexr.com/3d4ee
OK lets do it. I have come up with a devilish idea. If JS had look-behinds this could have been done simply by reversing the applied logic in the previous example where i had used a look-forward. Alas, there aren't... So i decided to turn the world the other way around. Check this out.
String.prototype.reverse = function(){
return this.split("").reverse().join("");
};
var rex = /[",]+(\w*)(?=[",\w]*"\[:"yrogetac)/g,
str = '{"device_types":["smartphone"],"isps":["a","B"],"network_types":[],"countries":[],"category":["Jebb","Bush","Donald","Trump"],"carriers":[],"exclude_carriers":[]}',
rev = str.reverse();
arr = [],
res = [];
while ((arr = rex.exec(rev)) !== null) {
res.push(arr[1].reverse()); // <- ["Trump", "Donald", "Bush", "Jebb"]
}
res.reverse(); // <- ["Jebb", "Bush", "Donald", "Trump"]
Just use your console to confirm.

Answer 5

In c++ you can do it like this
bool foundmatch = false;
try {
std::regex re("\"([a-zA-Z]+)\"*.:*.\\[[^\\]\r\n]+\\]");
foundmatch = std::regex_search(subject, re);
} catch (std::regex_error& e) {
// Syntax error in the regular expression
}

Answer 6

If the number of items in the array is limited (and manageable), you could define it with a finite number of optional items. Like this one with a maximum of 5 items:
"category":\["([^"]*)"(?:,"([^"]*)"(?:,"([^"]*)"(?:,"([^"]*)"(?:,"([^"]*)")?)?)?)?
regex101 example here.
Regards.