最近项目应要求，需要让textarea高度随输入自适应，那么走起吧！

html

<textarea></textarea>

css

textarea {
    width: 200px;
    height: 100px;
    min-height: 100px;
    overflow: hidden;
}

JS

/**
 * 让textarea高度随输入自适应
 * @param   {[[Type]]} selector 选择器
 * @param   {[[Type]]} callback
 */
var bindTextChange = function (selector, callback) {
    var $selector = $(selector);
    var _IE = (function() {
        var v = 3,
            div = document.createElement('div'),
            all = div.getElementsByTagName('i');
        while (
            div.innerHTML = '<!--[if gt IE ' + (++v) + ']><i></i><![endif]-->',
            all[0]
        );
        return v > 4 ? v : false;
    })();

    if (_IE && _IE < 9) {
        $selector.on('propertychange', function() {
            window.event.propertyName === 'value' && callback.call(this);
        });
    } else {
        $selector.on('input', callback);
        if (_IE === 9) {
            var callbackWrapper = function() {
                callback.call($selector[0]);
            }
            $selector.on('focus', function() {
                document.addEventListener('selectionchange', callbackWrapper);
            }).on('blur', function() {
                document.removeEventListener('selectionchange', callbackWrapper);
            });
        }
    }
}
var $textarea = $('textarea');
var paddingTop = parseFloat($textarea.css('padding-top'));
var paddingBottom = parseFloat($textarea.css('padding-bottom'));
var minHeight = parseFloat($textarea.css('min-height'));
bindTextChange('textarea', function() {
    $(this).height(minHeight).height(this.scrollHeight - paddingTop - paddingBottom);
});