You could get a JavaScript object containing the parameters with something like this:

var regex = /[?&]([^=#]+)=([^&#]*)/g,
url = window.location.href,
params = {},
match;
while(match = regex.exec(url)) {
params[match[1]] = match[2];
}

The regular expression could quite likely be improved. It simply looks for name-value pairs, separated by = characters, and pairs themselves separated by & characters (or an = character for the first one). For your example, the above would result in:

{v: "123", p: "hello"}

Here's a working example.

Today (2.5 years after this answer) you can safely use Array.forEach. As @ricosrealm suggests, decodeURIComponent was used in this function.

function getJsonFromUrl(url) {
if(!url) url = location.search;
var query = url.substr(1);
var result = {};
query.split("&").forEach(function(part) {
var item = part.split("=");
result[item[0]] = decodeURIComponent(item[1]);
});
return result;
}

actually it's not that simple, see the peer-review in the comments, especially:

  • hash based routing (@cmfolio)
  • array parameters (@user2368055)
  • proper use of decodeURIComponent and non-encoded = (@AndrewF)
  • non-encoded + (added by me)

For further details, see MDN article and RFC 3986.

Maybe this should go to codereview SE, but here is safer and regexp-free code:

function getJsonFromUrl(url) {
if(!url) url = location.href;
var question = url.indexOf("?");
var hash = url.indexOf("#");
if(hash==-1 && question==-1) return {};
if(hash==-1) hash = url.length;
var query = question==-1 || hash==question+1 ? url.substring(hash) :
url.substring(question+1,hash);
var result = {};
query.split("&").forEach(function(part) {
if(!part) return;
part = part.split("+").join(" "); // replace every + with space, regexp-free version
var eq = part.indexOf("=");
var key = eq>-1 ? part.substr(0,eq) : part;
var val = eq>-1 ? decodeURIComponent(part.substr(eq+1)) : "";
var from = key.indexOf("[");
if(from==-1) result[decodeURIComponent(key)] = val;
else {
var to = key.indexOf("]",from);
var index = decodeURIComponent(key.substring(from+1,to));
key = decodeURIComponent(key.substring(0,from));
if(!result[key]) result[key] = [];
if(!index) result[key].push(val);
else result[key][index] = val;
}
});
return result;
}

This function can parse even URLs like

var url = "?foo%20e[]=a%20a&foo+e[%5Bx%5D]=b&foo e[]=c";
// {"foo e": ["a a",  "c",  "[x]":"b"]}


var obj = getJsonFromUrl(url)["foo e"];
for(var key in obj) { // Array.forEach would skip string keys here
console.log(key,":",obj[key]);
}
/*
0 : a a
1 : c
[x] : b
*/