<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