var autoTextarea = function (elem, extra, maxHeight) {
    extra = extra || 20;
    var isFirefox = !!document.getBoxObjectFor || 'mozInnerScreenX' in window,
        isOpera = !!window.opera && !!window.opera.toString().indexOf('Opera'),
        addEvent = function (type, callback) {
            elem.addEventListener 
 
?
                elem.addEventListener(type, callback, false) :
                elem.attachEvent('on' + type, callback);
        },
        getStyle = elem.currentStyle ? function (name) {
            var val = elem.currentStyle[name];

            if (name === 'height' && val.search(/px/i) !== 1
 
) {
                var rect = elem.getBoundingClientRect();
                return rect.bottom - rect.top -
                    parseFloat(getStyle('paddingTop')) -
                    parseFloat(getStyle('paddingBottom')) + 'px';
            };

            return val;
        } : function (name) {
            
 
return getComputedStyle(elem, null)[name];
        },
        minHeight = parseFloat(getStyle('height'));

    elem.style.maxHeight = elem.style.resize = 'none';

    var change = function () {
        var scrollTop, height,
            padding = 0,
            style = elem.style;

        if (elem._length === elem.value.length) return;
        elem._length = elem.value.length;

        if (!isFirefox && !isOpera) {
            padding = parseInt(getStyle('paddingTop')) + parseInt(getStyle('paddingBottom'));
        };

        scrollTop = document.body.scrollTop || document.documentElement.scrollTop;

        elem.style.height = minHeight + 'px';
        if (elem.scrollHeight > minHeight) {
            if (maxHeight && elem.scrollHeight > maxHeight) {
                height = maxHeight - padding;
                style.overflowY = 'auto';
            } else {
                height = elem.scrollHeight - padding;
                style.overflowY = 'hidden';
            };

            style.height = height + extra + 'px';
            scrollTop += parseInt(style.height) - elem.currHeight;
            document.body.scrollTop = scrollTop;
            document.documentElement.scrollTop = scrollTop;
            elem.currHeight = parseInt(style.height);
        };
    };

    addEvent('propertychange', change);
    addEvent('input', change);
    addEvent('focus', change);
    change();
};
  
//讓文字域設定為自適應高度
function inittaByid(arr) {
    if (arr){
        for (var i = 0; i < arr.length ; i++) {
            autoTextarea(document.getElementById(arr[i]));
            $("#"+arr[i]).focus();
        }
        $(document).scrollTop(0);
    }
    
}

呼叫方法,傳元素id即可，為陣列格式的引數

inittaByid(["id1","id2"])