Javascript String replaceParam(uri, key, value)

"use strict";/*from www .  j  a va2  s . com*/

String.prototype.replaceParam = function (uri, key, value) {
    var re = new RegExp("([?|&])" + key + "=.*?(&|#|$)", "i");
    if (uri.match(re)) {
        return uri.replace(re, '$1' + key + "=" + value + '$2');
    } else {
        var hash =  '';
        if( uri.indexOf('#') !== -1 ){
            hash = uri.replace(/.*#/, '#');
            uri = uri.replace(/#.*/, '');
        }
        var separator = uri.indexOf('?') !== -1 ? "&" : "?";
        return uri + separator + key + "=" + value + hash;
    }
};