how to intercept innerHTML changes in javascript?
I need to intercept any changes in the content of a cell inside my webpage.
The following code shows me that addEventListener does not work.
function modifyText() {
alert("!");
}
var el=document.getElementById("mycell");
el.innerHTML="a"
el.addEventListener("change", modifyText, false);
// After next instruction I expect an alert message but it does not appear...
el.innerHTML="Z";
The code is just a toy example. In my real case the changes in the page (and therefore in the cell, too) are made by a webapp that I have NO control over.
There is a modern way to catch innerhtml changes:
https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver/observe
Example:
// identify an element to observe
elementToObserve = window.document.getElementById('y-range').children[0];
// create a new instance of 'MutationObserver' named 'observer',
// passing it a callback function
observer = new MutationObserver(function(mutationsList, observer) {
console.log(mutationsList);
});
// call 'observe' on that MutationObserver instance,
// passing it the element to observe, and the options object
observer.observe(elementToObserve, {characterData: false, childList: true, attributes: false});
childList mutation fires on innerHTML change.
You can’t listen to a DOM element change that way. change event is mostly for inputs
There is some other new DOM 3 events that would help you on this.
Here is some:
DOMCharacterDataModified //Draft
Does this Most efficient method of detecting/monitoring DOM changes? help?
It seems like there aren’t any 100% cross browser solutions, and one of the workarounds is to poll the elements of interest to see if their innerHTML.length changes!
