div simulate text entry boxes do word limit by words substr limit when the cursor reaches back to the beginning but will delete objects with range limit

<div class = "textarea textareaplace" id = "userinfo" contenteditable = "true" onkeydown = "keyD (this);" onkeyup = "keyAction (this);" oncopy = "keyCop ();" onpaste = "keyPas () "> </ div>

JS Code
var = TextBox document.getElementById ( 'UserInfo'),
g_selectNum = 0,
SEL = window.getSelection (),
Range = document.createRange ();
function keyD (obj) {// press event
var A = textbox.innerHTML;

var = TEXTA textbox.innerText.substr (0,20);
range.selectNodeContents (TextBox); // div node will add the contents of the range
range.collapse (to false);
sel.removeAllRanges ( );
sel.addRange (range); // J Object is added to the text field range
}
function keyPas () {
var TEXTA = textbox.innerText.substr (0,20);
setTimeout(function(){
var a=textbox.innerHTML;
textbox.innerText=a.replace(/<span.*">|<\/span>/g, "");   //将复制内容中span标签替换
range.selectNodeContents(textbox);
range.collapse(false);
sel.removeAllRanges();
sel.addRange(range);
},300)
};
function keyCop(obj){
var textA=textbox.innerText.substr(0,20);
a_num=textA.length;
var selectCon=sel.toString()；
g_selectNum=selectCon.length;
}
function keyAction(obj) {
var textA=textbox.innerText.substr(0,20);
a_num=textA.length;
a_arr[1]=a_num;
textbox.innerText=textA;
range.selectNodeContents(textbox);
range.collapse(false);
sel.removeAllRanges();
sel.addRange(range);
}