Randomly occurs with Meteor: "TypeError: Cannot read property 'invalidate' of undefined" -

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on seems random occasions, when user on website tries answer question on quiz page, following error occurs:

typeerror: cannot read property 'invalidate' of undefined @ tracker.dependency.changed (tracker.js:388) @ reactivevar.set (reactive-var.js:82) @ null. (builtins.js:22) @ view.js:191 @ function.template._withtemplateinstancefunc (template.js:437) @ view.js:190 @ object.blaze._withcurrentview (view.js:523) @ viewautorun (view.js:189) @ tracker.computation._compute (tracker.js:294) @ tracker.computation._recompute (tracker.js:313)

i unsure why occurs, , not entirely sure when error means if point me in right direction, great!

note: error seems occur when using chrome.

i'll hazard guess, here's culprit code in tracker.dependency

tracker.dependency.prototype.changed = function () {   var self = this;   (var id in self._dependentsbyid)     // comment - we're expecting `tracker.computation` has `.invalidate()` method!     self._dependentsbyid[id].invalidate(); };

so, problem something modifying object.prototype.

eg.

object.prototype.test = function(){} var emptyobj = {};  (i in emptyobj)    console.log('has key=', i, 'isownproperty?=', emptyobj.hasownproperty(i))

will print out:

has key= test isownproperty?= false

a possible solution try, adding snipped client, , seeing if fixes problem (at least temporarily):

tracker.dependency.prototype.changed = function () {   var self = this;   (var id in self._dependentsbyid){     if (self._dependentsbyid.hasownproperty(id)){       self._dependentsbyid[id].invalidate();     }   } }; tracker.dependency.prototype.hasdependents = function () {   var self = this;   for(var id in self._dependentsbyid)     if (self._dependentsbyid.hasownproperty(id))       return true;   return false; };

however - it's bad practice add object.prototype, , lots of code fail in unexpected ways. you'll need track down.


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