Safari convert '' (empty string) to 0 in URL

Question

We found unexpected behavior with URL object in safari. When you convert URL to string it will add 0 port(:0) if you set the port property to an empty string. e.g.

let url = new URL('https://www.example.com');
url.port = '';
console.log(url.toString()); // expected "https://www.example.com/", actual "https://www.example.com:0/"

From spec I see:

If the given value is the empty string, then set context object’s URL's port to null.

So is it bug or feature in safari?

Answer 1

I've also run into this. It's Web Kit Bug 127958 and at the time of writing almost 6 years old. The obvious workaround is to simply avoid assigning empty strings.

For example, if you have code like this:

template = new URL( template_url );
result = new URL( input_url );
for ( part in template ) {
    result[ part ] = template[ part ] ?? result[ part ];
}

You could instead do this:

template = new URL( template_url );
result = new URL( input_url );
for ( part in template ) {
    if ( template[ part ] && template[ part ] !== result[ part ] ) {
        result[ part ] = template[ part ];
    }
}