<div id="container">
        <textarea rows="1"></textarea>
    </div>

        * {
            padding: 0;
            margin: 0;
        }

        #container {
            width: 300px;
            padding: 10px;
            border: 1px solid #eee;
            box-sizing: border-box;
        }

        textarea {
            display: block;
            width: 100%;
            font-size: 20px;
            color: #000;
            line-height: 24px;
            outline: none;
            border: none;
            resize: none;
        }

 var textarea = document.querySelector('textarea')
        var inpnt = (function () {
            var baseHeight = null

            return function () {
                !baseHeight && (baseHeight = this.scrollHeight)
                this.rows = 1
                var rows = Math.ceil(this.scrollHeight / baseHeight) >= 3 ? 3 : Math.ceil(this
                    .scrollHeight / baseHeight)

                this.rows = rows
            }
        })()

        textarea.oninput = debounce(inpnt, 100)

        function debounce(func, delay) {
            var timer = null

            return function () {
                var _this = this
                var args = arguments

                timer && clearTimeout(timer)
                timer = setTimeout(function () {
                    func.apply(_this, args)
                }, delay)
            }
        }

                !baseHeight && (baseHeight = this.scrollHeight)
                this.rows = 1
                var rows = Math.ceil(this.scrollHeight / baseHeight) >= 3 ? 3 : Math.ceil(this
                    .scrollHeight / baseHeight)

 
                this.rows = rows