console
function addValue(){
document.getElementById("mytext").value='dfdsafdsfsfsdfsdfdsf';
init();
}
function addValue2(){
document.getElementById("mytext").value='哈哈哈哈';
}
init();
function changeValue(){
document.getElementById("webtest").value=document.getElementById("mytext").value;
}
function init(){
if("\v"=="v"){
document.getElementById("mytext").onpropertychange=changeValue;
}else{
document.getElementById("mytext").addEventListener("input",changeValue(),false);
}
}
<body>
<input type="button" id="txts" value="点击加载值!" onclick="addValue();"/>
<input type="button" id="txts2" value="第二次改加载值!" onclick="addValue2();"/>
<input type="text" name="textfield" id="mytext"/>
<div>您输入的值为:<input id="webtest"></input></div>
</body>