Regex pattern matching with various end points

Question

I'd like to extract substring, which has specific pattern, from following string list by javascript.

But I have problem in setting . 问题。

1. search?w=tot&DA=YZR&t__nil_searchbox=btn&sug=&o=& q=%EB%B9%84%EC%BD%98

2. search? q=%EB%B9%84%EC%BD%98 &go=%EC%A0…4%EB%B9%84%EC%BD%98&sc=8-2&sp=-1&sk=&cvid=f05407c5bcb9496990d2874135aee8e9

3. where=nexearch& query=%EB%B9%84%EC%BD%98 &sm=top_hty&fbm=0&ie=utf8

%EB%B9%84%EC%BD%98 for above cases.

/(query|q)=.* + + / + /

Its end point would be $ or first appeared &

What should I write for ? 写什么？

You can test it HERE . Thanks.

Answer 1

Turn the first capturing group to non-capturing group and then add a negated character class instead of .*

\b(?:query|q)=([^&\n]*)

DEMO

> var s = "where=nexearch& query=%EB%B9%84%EC%BD%98&sm=top_hty&fbm=0&ie=utf8"
undefined
> var pat = /\b(?:query|q)=([^&\n]*)/;
> pat.exec(s)[1]
'%EB%B9%84%EC%BD%98'

Answer 2

I'd personally suggest an alternate approach, using a more-procedural function to match the required parameter-values instead of a 'simple' regular expression. While it may look more complex at first, it does allow for easy extension should you need to find different, or additional, parameter values in future.

That said:

/* haystack:
     String, the string in which you're looking for the
     parameter-values,
   needles:
     Array, the parameters whose values you're looking for
*/
function queryGrab(haystack, needles) {
  // creating a regular expression from the array of needles,
  // given an array of ['q','query'], this will result in:
  // /^(q)|(query)/gi
  var reg = new RegExp('^(' + needles.join(')|(') + ')', 'gi'),

    // finding either the index of the '?' character in the haystack:
    queryIndex = haystack.indexOf('?'),

    // getting the substring from the haystack, starting
    // after the '?' character:
    keyValues = haystack.substring(queryIndex + 1)
      // splitting that string on the '&' characters,
      // to form an array:
      .split('&')
      // filtering that array (with Array.prototype.filter()),
      // the 'keyValue' argument is the current array-element
      // from the array over which we're iterating:
      .filter(function(keyValue) {
        // if RegExp.prototype.test() returns true,
        // meaning the supplied string ('keyValue')
        // is matched by the created regular expression,
        // the current element is retained in the filtered
        // array:
        return reg.test(keyValue);
    // converting that filtered-array to a string
    // on the naive assumption each searched-string
    // should return only one match:
    }).toString();

  // returning a substring of the keyValue, from after
  // the position of the '=' character:
  return keyValues.substring(keyValues.indexOf('=') + 1);
}

// essentially irrelevant, just for the purposes of
// providing a demonstration; here we get all the
// elements of class="haystack":
var haystacks = document.querySelectorAll('.haystack'),

  // the parameters we're looking for:
  needles = ['q', 'query'],

  // an 'empty' variable for later use:
  retrieved;

// using Array.prototype.forEach() to iterate over, and
// perform a function on, each of the .haystack elements
// (using Function.prototype.call() to use the array-like
// NodeList instead of an array):
Array.prototype.forEach.call(haystacks, function(stack) {
  // like filter(), the variable is the current array-element

  // retrieved caches the found parameter-value (using
  // a variable because we're using it twice):
  retrieved = queryGrab(stack.textContent, needles);

  // setting the next-sibling's text:
  stack.nextSibling.nodeValue = '(found: ' + retrieved + ')';

  // updating the HTML of the current node, to allow for
  // highlighting:
  stack.innerHTML = stack.textContent.replace(retrieved, '<span class="found">$&</span>');
});

 function queryGrab(haystack, needles) { var reg = new RegExp('^(' + needles.join(')|(') + ')', 'gi'), queryIndex = haystack.indexOf('?'), keyValues = haystack.substring(queryIndex + 1) .split('&') .filter(function(keyValue) { return reg.test(keyValue); }).toString(); return keyValues.substring(keyValues.indexOf('=') + 1); } var haystacks = document.querySelectorAll('.haystack'), needles = ['q', 'query'], retrieved; Array.prototype.forEach.call(haystacks, function(stack) { retrieved = queryGrab(stack.textContent, needles); stack.nextSibling.nodeValue = '(found: ' + retrieved + ')'; stack.innerHTML = stack.textContent.replace(retrieved, '<span class="found">$&</span>'); }); 

 ul { margin: 0; padding: 0; } li { margin: 0 0 0.5em 0; padding-bottom: 0.5em; border-bottom: 1px solid #ccc; list-style-type: none; width: 100%; } .haystack { display: block; color: #999; } .found { color: #f90; } 

 <ul> <li><span class="haystack">search?w=tot&amp;DA=YZR&amp;t__nil_searchbox=btn&amp;sug=&amp;o=&amp;q=%EB%B9%84%EC%BD%98</span> </li> <li><span class="haystack">search?q=%EB%B9%84%EC%BD%98&amp;go=%EC%A0…4%EB%B9%84%EC%BD%98&amp;sc=8-2&amp;sp=-1&amp;sk=&amp;cvid=f05407c5bcb9496990d2874135aee8e9</span> </li> <li><span class="haystack">where=nexearch&amp;query=%EB%B9%84%EC%BD%98&amp;sm=top_hty&amp;fbm=0&amp;ie=utf8</span> </li> </ul> 

JS Fiddle (for easier off-site experimentation) .

References:

• Array.prototype.filter() .
• Array.prototype.forEach() .
• Array.prototype.toString() .
• document.querySelectorAll() .
• Function.prototype.call() .
• RegExp() constructor .
• RegExp.prototype.test() .
• Regular Expression guide .
• String.prototype.indexOf() .
• String.prototype.split() .
• String.prototype.substring() .

Answer 3

Regexps are not the best way to parse these query strings. There are libraries and tools, but if you want to do it yourself:

function parseQueryString(url) {
    return _.object(url .              // build an object from pairs
        split('?')[1]   .              // take the part after the ?
        split('&')      .              // split it by &
        map(function(str) {            // turn parts into 2-elt array
            return str.split('=');     // broken at =
        })
    );
}

This uses Underscore's _.object , which creates an object from an array of arrays of key/value pairs, but if you don't want to use that, you can write your own equivalent in a couple of lines.

Now the value you are looking for is just

params = parseQueryString(url);
return params.q || params.query;