HTML String instances not handled as string

[[email protected]…]

JQuery does not (up till 1.8.1 at least) handle String instances as strings, but objects:

    >>> $(new String('<div>asdf</div>'));
    [ String ]

This test causes said behaviour:

    // Handle HTML strings
    if ( typeof selector === "string" ) {

and should read

    // Handle HTML strings
    if ( typeof selector === "string" || selector instanceof String ) {

or any other testing method for instance of a prototype / class.

This may not be the most important feature in the world, but it did surprise us when using a factory producing String instances and trying to append them to DOM through jQuery.

[[email protected]…]

As JSLint for example warns against using String as constructor, this might not be desired behaviour, but a clearer error about it would be appreciated, instead of

​http://jsfiddle.net/skmAm/1/

[sindresorhus]

You can just do

$('' + new String('<div>asdf</div>'));

[anonymous]

Replying to sindresorhus:

You can just do

$('' + new String('<div>asdf</div>'));

Yes, and we did fix this by changing the factory to return string primitives, but the point was that it required some not-so-obvious debugging, because the exceptions were unclear and browser dependent.

[dmethvin]

This isn't something we'd check for. In all places in the documentation we mean the primitive types and not the wrapped objects. A selector instanceof String check won't work for strings created in other frames, and the mere usage of it with some objects causes a ​memory leak in oldIE.

[jaubourg]

We should probably re-asses this for 2.0. Time for a $.isString?

[Christian Meixner <[email protected]…>]

And thats why jshint warns about it. Using new String() is not a good idea, because it causes a lot of weired behavior in JS. And you can not rely on the String object, because it will get lost on most operations, e.g:

typeof (new String('a')).toUpperCase() === 'string'

So it's better to not use it in the first place.

So I think this should not be fixed for the sake of jQuery's size and simplicity.

[dmethvin]

Yeah, this would ripple through the whole code base, not only String but Number and Boolean as well. Sorry it was so hard to debug, but this isn't a jQuery issue as much as a JavaScript one.

[[email protected]…]

Replying to dmethvin:

Yeah, this would ripple through the whole code base, not only String but Number and Boolean as well. Sorry it was so hard to debug, but this isn't a jQuery issue as much as a JavaScript one.

Fair enough. The reason for using it is a bit exotic anyway, and just modifying the final factory output to string primitive is a simple and clean solution.

Did not know about the 'instanceof' memoryleak in IE, it just keeps on coming up with new weirdness...