jQuery .trigger(event,args) barfs on {length:0} as handler argument

[marco@…]

Hi!

jQuery 1.8.3 until at least jQuery 2.0.3 mess up the handling of event-handler parameters supplied via .trigger, when the parameter is an object with a "length" property.

In line 4556 (jquery-2.0.3.js, function "trigger", line jQuery.makeArray( data, [ event ])) jQuery makes an array out of the parameter object (why in fks name?)... and according to a painful single-step trace, the length property is extended onto the "new" data local variable... which causes the argument to vanish entirely and the handler not recieving it (setting a.length=0 will wipe the array clean!).

A test case is available at ​http://jsfiddle.net/MGxqT/1/ (see the JS console!). This behavior is neither mentioned on the docs of .trigger() nor on the docs of .on().

Marco

[timmywil]

makeArray supports extending array-like objects (such as jQuery instances). However, we could ensure the object is not a plain object. I know we've gone round and round on this, but what are the team's thoughts?

[dmethvin]

I'm not sure whether any code does .trigger("click", arguments) but if it did any "fix" would break that. So I'm inclined to leave it as-is and document it.

There's an easy workaround, always put the object in an Array, like [ {length: 0} ]. You have to pass an array if you pass multiple args, but it was made optional for the single-arg case and that has been a pain in the butt ever since because of things like this.

[timmywil]

yea, agreed. Forgot about the arguments case.

[timmywil]

Docs issue: ​https://github.com/jquery/api.jquery.com/issues/377