Capture value out of query string with regex?

/name=([^&]*)/

• remove the ^ and end with an &

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Example:

var str     = "/pages/new?name=J&return_url=/page/new";
var matches = str.match(/name=([^&]*)/);
alert(matches[1]);

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The better way is to break all the params down (Example using current address):

function getParams (str) {
   var queryString = str || window.location.search || '';
   var keyValPairs = [];
   var params      = {};
   queryString     = queryString.replace(/.*?\?/,"");

   if (queryString.length)
   {
      keyValPairs = queryString.split('&');
      for (pairNum in keyValPairs)
      {
         var key = keyValPairs[pairNum].split('=')[0];
         if (!key.length) continue;
         if (typeof params[key] === 'undefined')
         params[key] = [];
         params[key].push(keyValPairs[pairNum].split('=')[1]);
      }
   }
   return params;
}


var url    = "/pages/new?name=L&return_url=/page/new";
var params = getParams(url);
params['name'];

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Update

Though still not supported in any version of IE, URLSearchParams provides a native way of retrieving values for other browsers.

The accepted answer includes the hash part if there is a hash right after the params. As @bishoy has in his function, the correct regex would be

/name=([^&#]*)/

here is the full function (tested and fixed for upper/lower case)

function getParameterByName (name) 
{
    name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
    var regexS = "[\\?&]" + name.toLowerCase() + "=([^&#]*)";
    var regex = new RegExp(regexS);
    var results = regex.exec(window.location.search.toLowerCase());
    if (results == null)
        return "";
    else
        return decodeURIComponent(results[1].replace(/\+/g, " "));
}

Improving on previous answers:

/**
 *
 * @param {string} name
 * @returns {string|null}
 */
function getQueryParam(name) {
  var q = window.location.search.match(new RegExp('[?&]' + name + '=([^&#]*)'));
  return q && q[1];
}

getQueryParam('a'); // returns '1' on page http://domain.com/page.html?a=1&b=2