In Firefox, traceur runtime causes performance-related warning

[louisremi]

Just loading the traceur-runtime in a page in Firefox (Nightly 35) causes the following warning to be logged in the console:

mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create

I've found some explanation about this message in this bug comment. The workaround seem to be to replace the use of proto with Object.create( otherClass.protototype ), see Object.create inheritance.

[arv]

Don't worry about it. We need to assign __proto__ to get the correct prototype chain for static inheritance.

Object.create does not work in our case because the instance needs to be a function instance.

[johnjbarton]

Or complain to Firefox about annoying messages.

On Mon, Sep 22, 2014 at 11:30 AM, Erik Arvidsson notifications@github.com
wrote:

Don't worry about it. We need to assign proto to get the correct
prototype chain for static inheritance.

Object.create does not work in our case because the instance needs to be
a function instance.

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#1367 (comment)
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[UltCombo]

Or complain to Firefox about annoying messages.

+1 to that. ;)

[louisremi]

I reopened a bug on bugzilla.mozilla.org and linked to this discussion, don't hesitate to chime in: https://bugzilla.mozilla.org/show_bug.cgi?id=1049041

[pflannery]

would this be avoided if we just used theObject.setPrototypeOf on latest browsers and for older browsers use this:

if (Object.setPrototypeOf === undefined) {
    Object.setPrototypeOf = function(oInstance, oProto) {
      oInstance.__proto__ = oProto;
      return oInstance;
    };
}

The example I grabbed from this page

I dont see many ref's to proto in the src and they all seem replaceable with setPrototypeOf

bearing in mind though I might be out of my league on this one :\