create super simple text editor use content editeble and javascript

editor.php

<div id='edit' >edit jjjjjjjj kkkjmlmlkmlkml  klknklnkn<div id="saya">saya</div> <div id="apa">apanya</div></div>
<button id="rubah">rubah</button>
<div id="result">ini hasil</div>


<script>
var edit = document.getElementById("edit");
var rubah = document.getElementById("rubah");
var result = document.getElementById("result");
edit.contentEditable = "true";
result.onclick = function(){
    var xh = new XMLHttpRequest();
    xh.onreadystatechange = function(){
       if(this.readyState == 4 && this.status == 200){
           edit.innerHTML = this.responseText;
       } 
    };
    xh.open("GET","edit.html",true);
    xh.send();
};

    rubah.addEventListener("click",function(){
        if(document.getSelection()){
            var a = document.getSelection();
            var b = a.getRangeAt(0);
            var d = b.startOffset;
            var e = b.endOffset;
            var c = a.toString();
            mh = edit.innerHTML.replace(c,"<div id='a' contenteditable='true' style='color:green;border:1px solid blue;padding:10px;'>" + c + "</div>");   
            var sx = new XMLHttpRequest();
            sx.onreadystatechange = function(){
                if(this.readyState == 4){
                    
                }
            };
            sx.open("GET","get.php?ee=" + mh,true);
            sx.send();
        }
    });
    
    var hj = edit.childNodes;
    for(i = 0;i < hj.length;i ++){
        hj[i].onclick = function(){
            result.innerHTML = this.id;
        }
    }
    
</script>