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);