让textarea高度随输入自适应

摘要：方法方法方法让高度随输入自适应文本框根据输入内容自适应高度输入框元素设置光标与输入框保持的距离默认设置最大高度可选使用方法利用插件

$("textarea").each(function () {
  this.setAttribute("style", "height:" + (this.scrollHeight) + "px;overflow-y:hidden;");
}).on("input", function () {
  this.style.height = "auto";
  this.style.height = (this.scrollHeight) + "px";
});

function setHeight(element) {
  $(element).css({"height":"auto","overflow-y":"hidden"}).height(element.scrollHeight);
}
$("textarea").each(function () {
  setHeight(this);
}).on("input", function () {
  setHeight(this);
});

/**
 * 文本框根据输入内容自适应高度
 * @param                {HTMLElement}        输入框元素
 * @param                {Number}                设置光标与输入框保持的距离(默认0)
 * @param                {Number}                设置最大高度(可选)
 */
function autoTextarea(elem, extra, maxHeight) {
  extra = extra || 0;
  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.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();
};

// 使用
// var address = document.getElementById("address");
// autoTextarea(address);

https://github.com/jackmoore/autosize