动态设置 textarea 的高度

    function makeExpandingArea(el) {
        var setStyle = function(el) {
            el.style.height = 'auto';
            el.style.height = el.scrollHeight + 'px';
            // console.log(el.scrollHeight);
        }
        var delayedResize = function(el) {
            window.setTimeout(function() {
                setStyle(el)
            },
            0);
        }
        if (el.addEventListener) {
            el.addEventListener('input',function() {
                setStyle(el)
            },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
        }
    }
   makeExpandingArea(textareaElement); 

 

 $("textarea").on("keydown",el,function(e) {
        e = e || window.event;
        var key = e.keyCode;
        if (key == 8 || key == 46) delayedResize(el);

    });
    $("textarea").on("cut",el,function(e) {
        delayedResize(el);
    });

    var timer = null;
    $(window).on("resize",function(){

        if(timer){
            clearTimeout(timer);
        }
        var wait = 50;
        timer = setTimeout(function(){
            $("textarea").each(function(){
                makeExpandingArea(this);
            });
        },wait);

    });