html文本域textarea高度自增、自动换行

文本域自动换行、高度自增，采用以下方式：

html:

<textarea rows="1" class="answerTextArea" maxlength="60"></textarea>

css:

.answerTextArea{
    width: 100%;
    height: auto;
    border:none;
    outline: none;
    font-size: 0.6rem;
    color:#fff;
    background: none;
    box-sizing: border-box;
    padding: 0.4rem 0;
    border-bottom: 1px solid #fff;
}

js实现功能：

//监听文本域输入，高度自动变化
function makeExpandingArea(el) {
   var timer = null;
   //由于ie8有溢出堆栈问题，故调整了这里
   var setStyle = function(el, auto) {
       if (auto) el.style.height = 'auto';
       el.style.height = el.scrollHeight + 'px';
   }
   var delayedResize = function(el) {
       if (timer) {
           clearTimeout(timer);
           timer = null;
       }
       timer = setTimeout(function() {
           setStyle(el)
       }, 200);
   }
   if (el.addEventListener) {
       el.addEventListener('input', function() {
           setStyle(el, 1);
       }, false);
       setStyle(el)
   } else if (el.attachEvent) {
       el.attachEvent('onpropertychange', function() {
           setStyle(el)
       })
       setStyle(el)
   }
   if (window.VBArray && window.addEventListener) { //IE9
       el.attachEvent("onkeydown", function() {
           var key = window.event.keyCode;
           if (key == 8 || key == 46) delayedResize(el);

       });
       el.attachEvent("oncut", function() {
           delayedResize(el);
       }); //处理粘贴
   }
}

//监听文本换行
function exeTextLine(obj){
    if(obj == ""){
        var textareaList = document.getElementsByClassName('answerTextArea');

        for(var i=0;i<textareaList.length;i++){
            makeExpandingArea(textareaList[i]);
        }
    }else{
        makeExpandingArea(obj);
    }

}

exeTextLine("");

效果如下：