JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu" class="menu">
  <input>
  test ok <button>ok</button>
  <label><input type="radio" name="test"> test</label>
  <label><input type="radio" name="test"> test</label>
</div>

<div class="editable" contenteditable>
<h4>
contenteditable area
</h4>
<p>
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad
minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in <img src="http://lorempizza.com/50/50" /> voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint...

CSS

pre {margin:0;}

.menu {
  border:1px solid blue;
}

JavaScript

Text.prototype.closest = function(s) {return this.parentNode.closest(s); }
Range.prototype.start = function(){return this.startContainer.childNodes[this.startOffset]};
var sel = document.getSelection();
Selection.prototype.getRange = function(){
	return sel.rangeCount?sel.getRangeAt(0):document.createRange();
}

Selection.prototype.setRange = function(r) {
	sel.removeAllRanges();
	sel.addRange(r);
}

if (/edge|chrom/i.test(navigator.userAgent)){ // beware, edge also put chrome in UA
	
	// ----  FIX for chrome, img not selected on click https://code.google.com/p/chromium/issues/detail?id=584334
	document.body.addEventListener('mousedown', e=>{
		if (e.target.tagName==='IMG' && e.target.closest('[contenteditable=true]')){
			//if (!e.target.parentNode) return console.log('what? img had no parent', e.target);
			sel.setRange(sel.selectNode(e.target));
		}
	});
}

document.addEventListener('selectionchange', e=>{
	console.log('sel change');
});

document.addEventListener('customselectionchange', e=>{
	console.log('CUSTOM selchange', e.detail.target && menu.contains(e.detail.target));
});


// ---------- for all browsers, a selectionchange events polyfill (includes event types, targets, ..)
	// document.addEventListener('selectionchange', emit); //does roughly the same than all below, without ^

// FF48 doesn't have selectionchange
let lastR = document.createRange();
function emit(e){
  let r = sel.getRange();
  if (r.compareBoundaryPoints(Range.START_TO_START, lastR)!==0 || 
      r.compareBoundaryPoints(Range.END_TO_END, lastR)!==0){
    document.dispatchEvent( new CustomEvent('customselectionchange', { detail: e }) );
  }
  lastR = r;
}
document.addEventListener('mousedown', e=>setTimeout(_=>emit(e)));
document.addEventListener('mouseup', e=>setTimeout(_=>emit(e)));
document.addEventListener('drop', emit);
document.addEventListener('mousemove', throttleImmediate(emit, 50));
document.addEventListener('keydown', throttleImmediate(emit,...