megawac / mutationobserver.js

ES3 Shim for the MutationObserver interface via DOM diffing.

MutationObserver

^{Note: the svg swapped the working browsers; IE8 works while IE7 fails 1 test}

A polyfill for the MutationObserver API (can I use?). The polyfill is more cause we can than should (with subtree at any rate)... It's async and uses a recursive timeout fallback (default checks changes every 30ms + runtime) instead of using the deprecated DOM3 MutationEvents so theoretically can support virtually any environment.

$ npm install mutationobserver-shim
$ bower install MutationObserver-shim

CDN

<script src="//cdn.jsdelivr.net/npm/mutationobserver-shim/dist/mutationobserver.min.js"></script>

Polyfill differences from standard interface

MutationObserver

• Implemented using a recursive setTimeout (every ~30 ms) rather than using a setImmediate polyfill; so calls will be made less frequently and likely with more data than the standard MutationObserver. In addition, it can miss changes that occur and then are lost in the interval window.
• Setting an observed elements html using innerHTML will call childList observer listeners with several mutations with only 1 addedNode or removed node per mutation. With the standard you would have 1 call with multiple nodes in addedNodes and removedNodes node lists.
• With childList and subtree changes in node order (eg first element gets swapped with last) should fire a addedNode and removedNode mutation but the correct node may not always be identified.

MutationRecord

• addedNodes and removedNodes are arrays instead of NodeLists
• oldValue is always called with attribute changes
• nextSibling and previousSibling correctfullness is questionable (hard to know if the order of appended items). I'd suggest not relying on them anyway (my tests are extremely permissive with these attributes)

Supported MutationObserverInit properties

Currently supports the following MutationObserverInit properties:

• childList: Set to truthy if mutations to target's immediate children are to be observed.
• subtree: Set to truthy to do deep scans on a target's children.
• attributes: Set to truthy if mutations to target's children are to be observed. As explained in #4, the style attribute may not be matched in ie<8.
• attributeFilter: Set to an array of attribute local names (without namespace) if not all attribute mutations need to be observed.
• attributeOldValue: doesn't do anything attributes are always called with old value
• characterData: currently follows Mozilla's implementation in that it will only watch textNodes values and not, like in webkit, where setting .innerHTML will add a characterData mutation.

Performance

By default, the polyfill will check observed nodes about 25 times per second (30 ms interval) for mutations. Try running these jsperf.com tests and the JSLitmus tests in the test suite for usage performance tests. It may be worthwile to adapt MutationObserver._period based on UA or heuristics (todo).

From my tests observing any size element without subtree enabled is relatively cheap. Although I've optimized the subtree check to the best of my abilities it can be costly on large trees. You can draw your own conclusions based on the JSLitmus and jsperf tests noting that you can expect the mo to do its check 28+ times a second (by default).

Although supported, I'd recommend against watching attributes on the subtree on large structures, as the check is complex and expensive on terrible hardware like my phone :(

The included minified file has been tuned for performance.

Compatibility

I've tested and verified compatibility in the following browsers + these Sauce browsers

• Internet Explorer 8 (emulated), 9, 10 in win7 and win8
• Firefox 4, 21, 24, 26 in OSX, win7 and win8
• Opera 11.8, 12.16 in win7
• "Internet" on Android HTC One V
• Blackberry 6.0.16

Try running the test suite and see some simple example usage:

• http://jsbin.com/suqewogone listen to images being appended dynamically
• http://jsbin.com/bapohopuwi autoscroll an element as new content is added

See http://dev.opera.com/articles/view/mutation-observers-tutorial/ for some sample usage.

mutationobserver.js's Issues

Added and remove nodes through off mutation record count

var div = document.createElement("div");
var a = document.createElement("a");
var b = document.createElement("b");
var c = document.createElement("i");
div.appendChild(a);
observer.observe(div, {
     childList: true
});
div.insertBefore(b, a);
div.insertBefore(c, a);

Calls with 3 mutations (thinks a moves position) instead of 2

Testing other interfaces

http://www.w3.org/TR/dom/#mutation-algorithms

• Document fragment should be tested
• Circular recursive structures?
• Processing instructions

Not working with SSR

Hi, it's not working with SSR because window is undefined. Please add a window && !window.MutationObserver check. Thanks!

Add support for Browserify

This line does not work in browserify, because this is not the window:

this.MutationObserver = this.MutationObserver || this.WebKitMutationObserver || (function(){/* ... */})(void 0);

Changing it to this works:

this.MutationObserver = window.MutationObserver || window.WebKitMutationObserver || (function(){/* ... */})(void 0);

ie7 Style Attributes don't register

Quirksmode calls .attributes compat "A bloody mess." We use indexed attributes (relevant section)... Here's some highlights of problems to address

• Do yourself a favour and don't use the indexed attributes array.
• IE7 and lower don't return the value of a style attribute.
• IE 5.5 doesn't return custom attributes, and initially gives the attribute value instead of an attribute object.
• IE7 and lower give null for style values.
• IE 5.5 initially gives the value of the attribute; not the attribute object.

//Issue
var attributeTest = document.createElement("i");
attributeTest.style.width = "140px";
attributeTest.attributes.style.value ~~ "width: 140px;" //normally (browser dependent case, semi etc)
//ie<7
attributeTest.attributes.style.value === "null" //shit...

bower.json malformed

Bower reports two errors with this package's bower.json:

bower invalid-meta  The "name" is recommended to be lowercase, can contain digits, dots, dashes
bower invalid-meta  The "main" field cannot contain minified files

Because of this, some commands like bower list won't work in projects where this package is installed.

Crashed in IE9 and IE8

I faced such issue in IE9 and IE8 during the integration of MutationObserver.JS to one of our projects. The MutationOserver object initialized with such preferences:

app.util.observeDOMModification($cache.loginPopup, {
    'attributes' : true,
    'attributeFilter' : [ 'height', 'style' ],
    'childList' : true,
    'subtree' : true
}, loginPopupModifiedHandler);

Please, take a look on screenshot, so you can see the actual error message and the place where it has been thrown.

Seems like the issue appears due not correct input parameter to the "reduce" function.

Could you please suggest the possible work around for such case?

Error: Cannot assign to read only property 'MutationObserver' of object '[object Object]' in SalesForce

Hi @megawac, I'm trying to use the Mutation Observer shim in my code which will run in SalesForce. The locker head console which checks the security of the script is logging errors from your polyfill. When I checked, the MutationObseerver which is read-only cannot be reassigned.
I have tested your minified file here.
The results were

With respect to this issue, I have created a PR.

Observing attributes or charData on subtree misses new elements

var observer = new MutationObserver($.noop);
observer.observe(document, {
    attributes: true,
    subtree: true
});
var $crossDocEl = $("body", document).append("<div id='test'>").find("#test");
observer.takeRecords();
$crossDocEl.attr("foo", "boo");
var records = observer.takeRecords();

// records === []

As new element test isn't observed!

TypeError: Cannot read property 'length' of undefined when observe(document, ...)

When I invoke

myObserver.observe(document, { attributes: true, characterData: true, childList: true, subtree: true });

I got the following errors

TypeError: Cannot read property 'length' of undefined
    at reduce (/Users/Ricky/Documents/gaia/node_modules/mutationobserver-shim/MutationObserver.js:537:40)
    at copy (/Users/Ricky/Documents/gaia/node_modules/mutationobserver-shim/MutationObserver.js:462:38)
    at clone (/Users/Ricky/Documents/gaia/node_modules/mutationobserver-shim/MutationObserver.js:479:11)
    at createMutationSearcher (/Users/Ricky/Documents/gaia/node_modules/mutationobserver-shim/MutationObserver.js:173:25)
    at Object.MutationObserver.MutationObserver.WebKitMutationObserver.MutationObserver.observe (/Users/Ricky/Documents/gaia/node_modules/mutationobserver-shim/MutationObserver.js:105:21)

I think problem arise from [1]. $target.attributes means document.attributes, but we don't have any document.attributes and throw error. We should give a empty object if someone try to observe document.

[1] https://github.com/megawac/MutationObserver.js/blob/master/MutationObserver.js#L462

Can't add event listener to addedNodes from mutations

Hi. I'm trying to attach handlers to addedNodes events. I test it in ie9, trying to get it working with 'a' elements. It's working on original MutationObserver (tested on latest chrome), but not on polyfill.
Here is my example code.

http://plnkr.co/edit/mJ2Hlw0PzI4ZSIdus6rq?p=preview

Thanks.

Sauce Labs browser matrix shows incorrect results

I've raised a corresponding question for Sauce Labs team
https://support.saucelabs.com/customer/en/portal/questions/13019208-browser-matrix-svg-doesn-t-represent-the-recent-results?new=13019208

Source map not included in release

The source map is not included in the release download and the bower/npm packages.

Failed to parse source map from '/xxx/dist/MutationObserver.js'

hey, I received a warning in the terminal console，as follows

warning  in ./node_modules/mutationobserver-shim/dist/mutationobserver.min.js

Module Warning (from ./node_modules/source-map-loader/index.js):
Failed to parse source map from '/Users/xxx/node_modules/mutationobserver-shim/dist/MutationObserver.js' file: Error: ENOENT: no such file or directory, open '/Users/xxx/node_modules/mutationobserver-shim/dist/MutationObserver.js'

Can you help me? I haven't found the answer anywhere else

Release 0.2.6?

There have been a number of commits and improvments since 0.2.5, including better modularization and fixes to #5 and #6. What work is involved in tagging a new release? This shim is a great help when testing with phantom-js, and I'd love to see a new release instead of just having to keep up to date with master.

characterData mutation not detected

Ref systemjs/systemjs/issues/1157. This shim silently breaks SystemJS as the characterData mutation used in its Promise polyfill is not detected:

        var scheduled;
        var node = document.createTextNode('');
        var o = new MutationObserverShim(run);
        o.observe(node, { characterData: true });

                // run is never called
        function run() {
            var f = scheduled;
            scheduled = void 0;
            f();
        }

        var i = 0;
        return function (f) {
            scheduled = f;
            node.data = (i ^= 1);
        };

The documentation seems to suggest that characterData mutations are handled, but looking at the code path I'm not sure how. Is the code above meant to work with the shim? Thanks!

Sauce tests borked

https://travis-ci.org/megawac/MutationObserver.js

Bower package

Is there any chance the library will be published as Bower package?

IE8 examples are not working

Hi,
I was looking for pollyfils like yours in IE8 to use it as DOMNodeInserted event, but when I started checking example in ie8 under windows 7 , I have discovered that those samples don't work at all, for instance image is loaded with errors.

IE<8 AttributeNamespaceURI is undefined

The attribute.namespaceURI will be undefined instead of null in IE<8. Currently unhandled here

Change license

Hey there, this module is being used as a subdependency of a module my project relies on. Unfortunately I'm working on a project that has strict license requirements, and requires me to only use modules that have one of the more common licenses (MIT, Apache 2.0, BSD-2/3 etc.)

Would you be open to changing the license on this project to something like MIT, that maintains the same spirit as the WTFPL, but is a little bit more broadly recognized? Thanks!

Support for subtree

Hi,

thanks a lot for the shim, it's very helpful.

Is there any way to get support for observing the subtree of a node? Observing childList only reports changes to immediate children of a node, but anything that happens further down remains undetected.

Thanks in advance.

IE8 attribute change detection fails if DOM object has a property with failing toString() method

Open the following demo in IE8 and observe the error http://output.jsbin.com/dinovu/

The problem here is in the fact that IE8 considers properties as attributes and calls toString() when you are trying to evaluate attribute value