How can I match multiple occurrences with a regex in JavaScript similar to PHP's preg_match_all()?

Adam_Franco_15872 0
Viewed 263979

I am trying to parse url-encoded strings that are made up of key=value pairs separated by either & or &.

The following will only match the first occurrence, breaking apart the keys and values into separate result elements:

var result = mystring.match(/(?:&|&)?([^=]+)=([^&]+)/)

The results for the string '1111342=Adam%20Franco&348572=Bob%20Jones' would be:

['1111342', 'Adam%20Franco']

Using the global flag, 'g', will match all occurrences, but only return the fully matched sub-strings, not the separated keys and values:

var result = mystring.match(/(?:&|&)?([^=]+)=([^&]+)/g)

The results for the string '1111342=Adam%20Franco&348572=Bob%20Jones' would be:

['1111342=Adam%20Franco', '&348572=Bob%20Jones']

While I could split the string on & and break apart each key/value pair individually, is there any way using JavaScript's regular expression support to match multiple occurrences of the pattern /(?:&|&)?([^=]+)=([^&]+)/ similar to PHP's preg_match_all() function?

I'm aiming for some way to get results with the sub-matches separated like:

[['1111342', '348572'], ['Adam%20Franco', 'Bob%20Jones']]

or 

[['1111342', 'Adam%20Franco'], ['348572', 'Bob%20Jones']]
javascript regex
15 Answers

Hoisted from the comments

2020 comment: rather than using regex, we now have URLSearchParams, which does all of this for us, so no custom code, let alone regex, are necessary anymore.

– Mike 'Pomax' Kamermans

Browser support is listed here https://caniuse.com/#feat=urlsearchparams

I would suggest an alternative regex, using sub-groups to capture name and value of the parameters individually and re.exec():

function getUrlParams(url) {
  var re = /(?:\?|&(?:amp;)?)([^=&#]+)(?:=?([^&#]*))/g,
      match, params = {},
      decode = function (s) {return decodeURIComponent(s.replace(/\+/g, " "));};

  if (typeof url == "undefined") url = document.location.href;

  while (match = re.exec(url)) {
    params[decode(match[1])] = decode(match[2]);
  }
  return params;
}

var result = getUrlParams("http://maps.google.de/maps?f=q&source=s_q&hl=de&geocode=&q=Frankfurt+am+Main&sll=50.106047,8.679886&sspn=0.370369,0.833588&ie=UTF8&ll=50.116616,8.680573&spn=0.35972,0.833588&z=11&iwloc=addr");

result is an object:

{
  f: "q"
  geocode: ""
  hl: "de"
  ie: "UTF8"
  iwloc: "addr"
  ll: "50.116616,8.680573"
  q: "Frankfurt am Main"
  sll: "50.106047,8.679886"
  source: "s_q"
  spn: "0.35972,0.833588"
  sspn: "0.370369,0.833588"
  z: "11"
}

The regex breaks down as follows:

(?:            # non-capturing group
  \?|&         #   "?" or "&"
  (?:amp;)?    #   (allow "&", for wrongly HTML-encoded URLs)
)              # end non-capturing group
(              # group 1
  [^=&#]+      #   any character except "=", "&" or "#"; at least once
)              # end group 1 - this will be the parameter's name
(?:            # non-capturing group
  =?           #   an "=", optional
  (            #   group 2
    [^&#]*     #     any character except "&" or "#"; any number of times
  )            #   end group 2 - this will be the parameter's value
)              # end non-capturing group
Tomalak_187710

You need to use the 'g' switch for a global search

var result = mystring.match(/(&|&)?([^=]+)=([^&]+)/g)
meouw_121610

Set the g modifier for a global match:

/…/g
Gumbo_531140

Hеllo from 2020. Let me bring String.prototype.matchAll() to your attention:

let regexp = /(?:&|&)?([^=]+)=([^&]+)/g;
let str = '1111342=Adam%20Franco&348572=Bob%20Jones';

for (let match of str.matchAll(regexp)) {
    let [full, key, value] = match;
    console.log(key + ' => ' + value);
}

Outputs:

1111342 => Adam%20Franco
348572 => Bob%20Jones
user_27507430

Splitting it looks like the best option in to me:

'1111342=Adam%20Franco&348572=Bob%20Jones'.split('&').map(x => x.match(/(?:&|&)?([^=]+)=([^&]+)/))
user_9660230

To avoid regex hell you could find your first match, chop off a chunk then attempt to find the next one on the substring. In C# this looks something like this, sorry I've not ported it over to JavaScript for you.

        long count = 0;
        var remainder = data;
        Match match = null;
        do
        {
            match = _rgx.Match(remainder);
            if (match.Success)
            {
                count++;
                remainder = remainder.Substring(match.Index + 1, remainder.Length - (match.Index+1));
            }
        } while (match.Success);
        return count;
user_26688690
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