How to retrieve GET parameters from javascript?

http://domain.com/page.html?returnurl=%2Fadmin

For
js within page.html,how can it
retrieve GET
parameters?

For the above simple
example,func('returnurl') should be
/admin

But it should
also work for complex querystrngs...

class="post-text" itemprop="text">

class="normal">Answer

With the
rel="noreferrer">window.location object. This code gives you GET without
the question
mark.

window.location.search.substr(1)

From
your example it will return
returnurl=%2Fadmin

EDIT:
I took the liberty of changing href="https://stackoverflow.com/a/21210643/179669">Qwerty's answer, which
is really good, and as he pointed I followed exactly what
the OP asked:

function
            findGetParameter(parameterName) {
 var result = null,
 tmp =
            [];
 location.search
 .substr(1)


            .split("&")
 .forEach(function (item) {
 tmp =
            item.split("=");
 if (tmp[0] === parameterName) result =
            decodeURIComponent(tmp[1]);
 });
 return
            result;
}

I
removed the duplicated function execution from his code, replacing it a variable ( tmp )
and also I've added href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURIComponent"
rel="noreferrer">decodeURIComponent, exactly as OP
asked. I'm not sure if this may or may not be a security
issue.

Or otherwise with plain for
loop, which will work even in
IE8:

function
            findGetParameter(parameterName) {
 var result = null,
 tmp =
            [];
 var items = location.search.substr(1).split("&");
 for (var
            index = 0; index < items.length; index++) {
 tmp =
            items[index].split("=");
 if (tmp[0] === parameterName) result =
            decodeURIComponent(tmp[1]);

 }
 return
            result;
}