Question

I’ve found plenty of articles on StackOverflow that mention fast ways to parse query string’s in Javascript, but what I haven’t found is how to handle both & and ; as a delimiter.

Now, I assume, only one of those gets set as the delimiter for the query string. Take for instance, the following query string:

index.php?Param1=value&Param2=value;Param3=value

Which is the delimiter?

• Is it &, or is it ;?
• Is it the first recognized delimiting character, or is it & takes precedence over ;?
• Are both treated as delimiters, and all three parameters from the example parsed?

In Javascript, I have historically been using the following function:

/**
 * Gets the value of a parameter from a URI.
 * @param href The full URI to search. Must at least start with a ? query string delimiter.
 * @param key  The key of the param for which to retrieve the value.
 * @param def  A default value to return in the case that the key cannot be found in the query string.
 * @return The value of the param if the key is found, otherwise returns def.
 */
function getURIParam(href, key, def) {
    if (arguments.length == 2) def = null;

    var qs = href.substring(href.indexOf('?') + 1);
    var s = qs.split('&');
    for (var k in s) {
        var s2 = s[k].split('=');
        if (s2[0] == key)
            return decodeURIComponent(s2[1]);
    }

    return def;
}

That just splits out each key/value pair based on &. It works great, so long as the delimiter is always &. As we know, however, that is not always the case, nor should be enforced, as the RFC allows for ; as well.

So, in order to handle both & and ; as a delimiter, should I first search for an indexOf("&") and if no occurrence is found, set the delimiter to ;?

What is the proper way of parsing a URL based on the rule that the delimiter can be either & or ;?

Here is the W3C Recommendation on server being able to handle both & and ;.

We recommend that HTTP server implementors, and in particular, CGI
implementors support the use of “;” in place of “&” to save authors
the trouble of escaping “&” characters in this manner.

Here is RFC 1738 which defines the URI.

Answer 1

You can use reg ex to split on two delimiters.

var s = qs.split(/[&;]/)

This will handle strings with both & and ;

Edit:

here is a post to split on one or the other given the first occurence of the character. Hopefully the URL contains the semicolon first but it might be safer to check for any occurrence of ; and just using that as the delimiter if present.

According to RFC3986 it is up to the scheme implementor to decide on how the usage of the URI reserved characters is to be used. Also According to RFC 1738, semi-colon is a reserved character in the search part of a URI, and as such, if present, is treated as a delimiter, unless encoded.The W3C recommends that server implementers allow both to allow developers to not have to escape the ampersand, therefore one or the other should be used.

I would intrepid your example of

index.php?Param1=value&Param2=value;Param3=value

as

["Param1=value&Param2=value","Param3=value"]