div模拟textarea在ios下不兼容的问题解决

今天发现一个好东西，赶紧记下来，我在用textarea的时候，想要自适应高度，这样就不会出现滚动条。网上找了很多，都是用div模拟的，但是好扯淡，div模拟的在ios下不能聚焦并且不能输入。真坑。。。。

然后找了很久，发现了下面这个好东西，嘿嘿嘿，我给你看个宝贝。

这个就不需要去模拟啦，可以直接使用textarea。

(function (root, factory) {
      'use strict';

      if (typeof define === 'function' && define.amd) {
        // AMD. Register as an anonymous module.
        define([], factory);
      } else if (typeof exports === 'object') {
        // Node. Does not work with strict CommonJS, but
        // only CommonJS-like environments that support module.exports,
        // like Node.
        module.exports = factory();
      } else {
        // Browser globals (root is window)
        root.autosize = factory();
      }
    }(this, function () {
      function main(ta) {
        if (!ta || !ta.nodeName || ta.nodeName !== 'TEXTAREA' || ta.hasAttribute('data-autosize-on')) { return; }

        var maxHeight;
        var heightOffset;

        function init() {
          var style = window.getComputedStyle(ta, null);

          if (style.resize === 'vertical') {
            ta.style.resize = 'none';
          } else if (style.resize === 'both') {
            ta.style.resize = 'horizontal';
          }

          // horizontal overflow is hidden, so break-word is necessary for handling words longer than the textarea width
          ta.style.wordWrap = 'break-word';

          // Chrome/Safari-specific fix:
          // When the textarea y-overflow is hidden, Chrome/Safari doesn't reflow the text to account for the space
          // made available by removing the scrollbar. This workaround will cause the text to reflow.
          var width = ta.style.width;
          ta.style.width = '0px';
          // Force reflow:
          /* jshint ignore:start */
          ta.offsetWidth;
          /* jshint ignore:end */
          ta.style.width = width;

          maxHeight = style.maxHeight !== 'none' ? parseFloat(style.maxHeight) : false;
          
          if (style.boxSizing === 'content-box') {
            heightOffset = -(parseFloat(style.paddingTop)+parseFloat(style.paddingBottom));
          } else {
            heightOffset = parseFloat(style.borderTopWidth)+parseFloat(style.borderBottomWidth);
          }

          adjust();
        }

        function adjust() {
          var startHeight = ta.style.height;
          var htmlTop = document.documentElement.scrollTop;
          var bodyTop = document.body.scrollTop;
          
          ta.style.height = 'auto';

          var endHeight = ta.scrollHeight+heightOffset;

          if (maxHeight !== false && maxHeight < endHeight) {
            endHeight = maxHeight;
            if (ta.style.overflowY !== 'scroll') {
              ta.style.overflowY = 'scroll';
            }
          } else if (ta.style.overflowY !== 'hidden') {
            ta.style.overflowY = 'hidden';
          }

          ta.style.height = endHeight+'px';

          // prevents scroll-position jumping
          document.documentElement.scrollTop = htmlTop;
          document.body.scrollTop = bodyTop;

          if (startHeight !== ta.style.height) {
            var evt = document.createEvent('Event');
            evt.initEvent('autosize.resized', true, false);
            ta.dispatchEvent(evt);
          }
        }

        // IE9 does not fire onpropertychange or oninput for deletions,
        // so binding to onkeyup to catch most of those events.
        // There is no way that I know of to detect something like 'cut' in IE9.
        if ('onpropertychange' in ta && 'oninput' in ta) {
          ta.addEventListener('keyup', adjust);
        }

        window.addEventListener('resize', adjust);
        ta.addEventListener('input', adjust);

        ta.addEventListener('autosize.update', adjust);

        ta.addEventListener('autosize.destroy', function(style){
          window.removeEventListener('resize', adjust);
          ta.removeEventListener('input', adjust);
          ta.removeEventListener('keyup', adjust);
          ta.removeEventListener('autosize.destroy');

          Object.keys(style).forEach(function(key){
            ta.style[key] = style[key];
          });

          ta.removeAttribute('data-autosize-on');
        }.bind(ta, {
          height: ta.style.height,
          overflow: ta.style.overflow,
          overflowY: ta.style.overflowY,
          wordWrap: ta.style.wordWrap,
          resize: ta.style.resize
        }));

        ta.setAttribute('data-autosize-on', true);
        ta.style.overflow = 'hidden';
        ta.style.overflowY = 'hidden';

        init();   
      }

      // Do nothing in IE8 or lower
      if (typeof window.getComputedStyle !== 'function') {
        return function(elements) {
          return elements;
        };
      } else {
        return function(elements) {
          if (elements && elements.length) {
            Array.prototype.forEach.call(elements, main);
          } else if (elements && elements.nodeName) {
            main(elements);
          }
          return elements;
        };
      }
    }));
引入上面的js，然后在需要用的页面执行下面这行代码
　　autosize(document.querySelectorAll('textarea'));

如果不想出现滚动条，就设置一个max-height，不设置的话，还是会出现滚动条滴