Detect Element.Style changes with Javascript

Question

I am at the moment working on a little extension to enhance a website namely the google plus post box. I want to move it to the very left of the monitor.

This post box however resets its values every time it is opened.

Basically I would like to kill off that behavior, and thought I could just monitor the element for element.style changes, and overwrite them again. However DOMAttrModified seems not to work for stuff like that

Additionally to that I have found that when the post box is closed it ceases to exist oO?

Maybe someone here has an idea how to tackle this I could of course just loop an operation that sets the style every second or so. but no thanks XD

thanks a lot for helping :)

Answer 1

Mutation events are deprecated, DOMAttrModified is not and will not be supported by webkit browsers. Use Mutation Observers instead. Alternatively, you can try this workaround .

Answer 2

To get you quickly started with using Mutation Observer
here's a small reusable function

/**
 * Mutation Observer Helper function
 * //developer.mozilla.org/en-US/docs/Web/API/MutationObserver/observe
 * @param {string} sel The DOM selector to watch 
 * @param {object} opt MutationObserver options 
 * @param {function} cb Pass Mutation object to a callback function
 */
const Observe = (sel, opt, cb) => {
  const Obs = new MutationObserver((m) => [...m].forEach(cb));
  document.querySelectorAll(sel).forEach(el => Obs.observe(el, opt));
};

To track only attribute "style" changes on some class="item" Elements, use like :

Observe(".item", {
  attributesList: ["style"], // Only the "style" attribute
  attributeOldValue: true,   // Report also the oldValue
}, (m) => {
  console.log(m);            // Mutation object
});

To watch for all attributes changes, instead of the attributesList Array use :

attributes: true

If needed, here's an example:

 /** * Mutation Observer Helper function * //developer.mozilla.org/en-US/docs/Web/API/MutationObserver/observe * @param {string} sel The DOM selector to watch * @param {object} opt MutationObserver options * @param {function} cb Pass Mutation object to a callback function */ const Observe = (sel, opt, cb) => { const Obs = new MutationObserver((m) => [...m].forEach(cb)); document.querySelectorAll(sel).forEach(el => Obs.observe(el, opt)); }; // DEMO TIME: Observe("#test", { attributesList: ["style"], attributeOldValue: true, }, (m) => { console.log(` Old value: ${m.oldValue} New value: ${m.target.getAttribute(m.attributeName)} `); }); const EL_test = document.querySelector("#test"); EL_test.addEventListener("input", () => EL_test.style.cssText = EL_test.value); EL_test.style.cssText = EL_test.value;

 * {margin:0;} textarea {width: 60%;height: 50px;}

 <textarea id="test"> background: #0bf; color: #000; </textarea>