How to retrieve GET parameters from JavaScript [duplicate]

Question

Consider:

http://example.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 query strings...

Answer 1

With the 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 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 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; }