Is a url query parameter valid if it has no value?

Question

Is a url like http://example.com/foo?bar valid?

I\'m looking for a link to something official that says one way or the other. A simple yes/no answer or

Answer 1

As all other answers described, it's perfectly valid for checking, specially for boolean kind stuff

Here is a simple function to get the query string by name:

function getParameterByName(name, url) {
    if (!url) {
        url = window.location.href;
    }
    name = name.replace(/[\[\]]/g, "\\$&");
    var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
        results = regex.exec(url);
    if (!results) return null;
    if (!results[2]) return '';
    return decodeURIComponent(results[2].replace(/\+/g, " "));
}

and now you want to check if the query string you are looking for exists or not, you may do a simple thing like:

var exampleQueryString = (getParameterByName('exampleQueryString') != null);

the exampleQueryString will be false if the function can't find the query string, otherwise will be true.

Answer 2

It is valid: see Wikipedia, RFC 1738 (3.3. HTTP), RFC 3986 (3. Syntax Components).