Need explanation on Javascript regex request parameter parsing

Question

Examples first, questions second...

Example 1) Non global match of '?sort=alpha&direction=asc'

'?sort=alpha&direction=asc'.match(/([^?&=]+)(=([^&]*))?/);

Output:

// ['sort=alpha', 'sort', '=alpha', 'alpha']

Example 2) Global match of '?sort=alpha&direction=asc'

'?sort=alpha&direction=asc'.match(/([^?&=]+)(=([^&]*))?/g);

Output:

// ['sort=alpha', 'sort', '=alpha', 'alpha']

Example 3) Global match replace of '?sort=alpha&direction=asc'

getRequestParameters: function () {
    var query_string = {},
        regex = new RegExp('([^?=&]+)(=([^&]*))?', 'g');

    '?sort=alpha&direction=asc'.replace(regex, function(match, p1, p2, p3, offset, string) {
        console.log(match, p1, p2, p3, offset, string);

        query_string[p1] = p3;
    });
}

Output:

// sort=alpha sort =alpha alpha 1 ?sort=alpha&direction=asc
// direction=asc direction =asc asc 12 ?sort=alpha&direction=asc 

My Questions

I am not sure if I could have ever figured this one out on my own, but I never "live" with a solution and I must figure out the rhyme behind the reason. The specific matches I think understand "fully enough". I believe I know some of the answers below, but I rather not make assumptions and learn from smarter people!

1. Why are 1) and 2) the same? (or are they?)
2. What does the 'sort=alpha' mean in 1) and 2)?
3. Why does 2) not return both sort and direction parameters?
4. What is the 3) iterating over with the .replace()?
5. Is there a way of capturing N parameters without .replace()?

Thanks!

update

var regex = new RegExp('([^?&=]+)(=([^&]*))?');
regex.exec('?sort=alpha&direction=asc');
// Chrome 21 - ["sort=alpha", "sort", "=alpha", "alpha"]

var regex = new RegExp('([^?&=]+)(=([^&]*))?', 'g');
regex.exec('?sort=alpha&direction=asc');
// Chrome 21 - ["sort=alpha", "sort", "=alpha", "alpha"]

'?sort=alpha&direction=asc'.match(/([^?&=]+)(=([^&]*))?/);
// Chrome 21 - ["sort=alpha", "sort", "=alpha", "alpha"]

'?sort=alpha&direction=asc'.match(/([^?&=]+)(=([^&]*))?/g);
// Chrome 21 - ["sort=alpha", "direction=asc"]

var regex = new RegExp('([^?&=]+)(=([^&]*))?', 'g');
regex.lastIndex = 11;
regex.exec('?sort=alpha&direction=asc');
// Chrome 21 - ["direction=asc", "direction", "=asc", "asc"]

In summary, Example 3) is still correct, but go to this answer for a more qualified response.

end update

References and thanks to Steven Benner:

• https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/match
• https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/replace
• http://stevenbenner.com/2010/03/javascript-regex-trick-parse-a-query-string-into-an-object/
• http://www.bloggingdeveloper.com/post/JavaScript-QueryString-ParseGet-QueryString-with-Client-Side-JavaScript.aspx (similar topic so I threw it in)

Answer 1

Answers first, question afterwards:

1. In both Chrome 21 and Firefox 14 I get ["sort=alpha", "direction=asc"] for the g version - so they are not the same at all.
2. The first returned value from match is the entire matched string (in this case one or more characters that are not an ampersand, question mark or equal sign optionally followed by an equal sign and zero or more characters that are not an ampersand).
3. It does (see answer to #1) - what browser are you running these tests in?
4. replace is iterating over each match it finds in the string.

5. Use multiple calls to exec or use the existing regex you have:

   > '?sort=alpha&direction=asc&another=value'.match(/([^?&=]+)(=([^&]*))?/g);
   ["sort=alpha", "direction=asc", "another=value"]
   

What browser are you using that gave you the results you provided for your first questions?