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#5319 closed bug ()

Opened October 02, 2009 05:38PM UTC

Closed November 11, 2010 11:09PM UTC

Error when passing new String(...) to jQuery.html()

Reported by: bartaz Owned by:
Priority: major Milestone: 1.4
Component: core Version: 1.3.2
Keywords: Cc: bartaz
Blocked by: Blocking:

I found this error when passing a String object to $.fn.html.

The simple case looks like this:

$("div").html(new String("test"));

This code throws an error, reported by Firebug as:

''Could not convert JavaScript argument arg 0 [nsIDOMDocumentFragment.appendChild]''

I tracked it down to find that problems seem to be in jQuery.clean function.

Strings created from String() constructor have typeof 'object' so are not recognized as strings. So this condition in clean method falis:

// Convert html string into DOM nodes
if ( typeof elem === "string" ) { ... }
Attachments (0)
Change History (6)

Changed October 02, 2009 08:36PM UTC by flesler comment:1

cc: → bartaz
component: unfilledcore
need: ReviewTest Case

Can you provide a test case where you'd pass an objectified string instead of a native one ?

Changed October 02, 2009 09:33PM UTC by bartaz comment:2

I know that using objectified strings is probably not a common case, especially that they get 'stringified' again when concatenated with literal strings:

new String("test") + ""

In my case issue was caused by function extending String prototype.

It was 'truncate' function (taken from prototype.js)

String.prototype.truncate = function(length, truncation) {
    length = length || 30;
    truncation = truncation === undefined ? '...' : truncation;
    return this.length > length ?
        this.slice(0, length - truncation.length) + truncation : this;

Let's say I used it like this:


Everything was fine when

was a string longer than 20 chars. It got truncated and displayed. But when it was shorter than 20 chars (so the truncate method returned
) the return value was a String object and
function failed to run.

Whenever you return

from extended String prototype it returns object, not literal string. So simple test case may be function that does 'nothing':

String.prototype.self = function(){ return this; }

What it actuality does is turning literal strings into String objects

I created a page where I run these cases:

I know that's not a common issue and it has easy workaround (concatenating with empty "" string before putting into


Changed October 03, 2009 12:33AM UTC by dmethvin comment:3

Interesting...i've never returned

explicitly when adding a method but I see what you mean. In general I avoid creating String or Number objects like the plague. There are a few cases where Javascript itself won't accept String objects but will accept literal strings. One that I recall is the argument to

If you have your method return

instead of
it will solve the problem.

This is somewhat similar to #4533 but that one seems easier to fix.

Changed October 03, 2009 06:31AM UTC by bartaz comment:4

Ok, I think it's quite fair to assume that the bug is in 'truncate' function that should return literal strings in both cases.

But when using additional JS libraries sometimes you don't know if you will always get literal (not object) strings and may be surprised when passing them into jQuery.

It seems to be quite easy to fix, so would be nice to have.

Changed October 14, 2010 03:14AM UTC by snover comment:5

status: newpending

This ticket has been marked as missing a test case. In an effort to reduce the number of outstanding tickets in the bug tracker, it will be closed automatically in 30 days. In order to prevent this from happening, please provide a working test case. If a test case has already been provided and our records are wrong, please respond to the ticket so that it can be fixed. Thank you!

Changed November 11, 2010 11:09PM UTC by trac-o-bot comment:6

status: pendingclosed

Automatically closed due to 14 days of inactivity.