如何用纯javascript检测textarea大小的变化？

Question

我想在textarea的大小发生变化时发出通知,当时发生了什么事,我该如何检测呢？

Answer 1

这是一个使用纯Javascript（无jQuery等依赖项）的小示例。

它使用mouseup和keyup处理程序以及可选的intervall来检测更改。

var detectResize = (function() {

  function detectResize(id, intervall, callback) {
    this.id = id;
    this.el = document.getElementById(this.id);
    this.callback = callback || function(){};

    if (this.el) {
      var self = this;
      this.width = this.el.clientWidth;
      this.height = this.el.clientHeight;

      this.el.addEventListener('mouseup', function() {
        self.detectResize();
      });

      this.el.addEventListener('keyup', function() {
        self.detectResize();
      });

      if(intervall) setInterval(function() {
          self.detectResize();
      }, intervall);

    }
    return null;
  }

  detectResize.prototype.detectResize = function() {
      if (this.width != this.el.clientWidth || this.height != this.el.clientHeight) {
        this.callback(this);
        this.width = this.el.clientWidth;
        this.height = this.el.clientHeight;
      }
  };

  return detectResize;

})();

用法： new detectResize(element-id, intervall in ms or 0, callback function)

例：

<textarea id="mytextarea"></textarea>
<script type="text/javascript">
var mytextarea = new detectResize('mytextarea', 500, function() {
  alert('changed');
});
</script>

可以在jsfiddle.net/pyaNS上看到它。

Answer 2

试试这个演示。

http://jsfiddle.net/vol7ron/Z7HDn/

jQuery(document).ready(function(){
   var $textareas = jQuery('textarea');

   // set init (default) state   
   $textareas.data('x', $textareas.outerWidth());
   $textareas.data('y', $textareas.outerHeight()); 

   $textareas.mouseup(function(){

      var $this = jQuery(this);

      if (  $this.outerWidth()  != $this.data('x') 
         || $this.outerHeight() != $this.data('y') )
      {
          alert( $this.outerWidth()  + ' - ' + $this.data('x') + '\n' 
               + $this.outerHeight() + ' - ' + $this.data('y')
               );
      }

      // set new height/width
      $this.data('x', $this.outerWidth());
      $this.data('y', $this.outerHeight()); 
   });

});

无法用纯 JavaScript 实现，我们必须使用jQuery