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improve performance for template repeat over model objects with shared prototype #74

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improve performance for template repeat over model objects with shared prototype #74

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15 changes: 13 additions & 2 deletions src/observe.js
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Original file line number Diff line number Diff line change
Expand Up @@ -608,6 +608,8 @@

var observedSetCache = [];

var hasOwnProperty = Object.prototype.hasOwnProperty;

function newObservedSet() {
var observerCount = 0;
var observers = [];
Expand All @@ -619,15 +621,24 @@
if (!obj)
return;

if (obj === rootObj)
var observeProto = true;
if (obj === rootObj) {
rootObjProps[prop] = true;

// If we find the property on the root object, we can skip observing
// the prototype, which is expensive. This helps a common use case:
// when the user has <template repeat> over items that all share a
// prototype. See https://github.com/Polymer/polymer-dev/issues/101
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Do we need to handle the case where the own property gets deleted?

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good call, I should at least have a test for that & mention it the comment. It should work because whenever it gets a change record (in callback below), it will rescan everything.

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i think that will work since we'll run through this code path in that case again and object will no longer have the own-property -- but a test would be ideal.

observeProto = !hasOwnProperty.call(rootObj, prop);
}

if (objects.indexOf(obj) < 0) {
objects.push(obj);
Object.observe(obj, callback);
}

observe(Object.getPrototypeOf(obj), prop);
if (observeProto)
observe(Object.getPrototypeOf(obj), prop);
}

function allRootObjNonObservedProps(recs) {
Expand Down