jQuery1.6c新增的适配器

其实在jQuery1.5中已有这东西，cssHooks，或者更早之前的 jQuery.event.special, 或者 Sizzle.selectors里面更多的对象。它们共同的特点是包含了许多相关的函数，cssHooks是专门处理css属性的获取与设置，如IE的 opacity,event.special用于装载与卸载submit, change, focus ,mouseenter等特别事件与自定义事件， Sizzle.selectors里面的过滤器与候选集获取器就更不用说了。由于JS用对象做为表进行查找是比if条句与switch语句快很多，加之， 适配器这种模式对于扩展新功能非常有利，因为jQuery1.6便把它发扬光大了。

在jQuery的attributes模块（github是这样分割的，但耦合这么高很难说是模块），共增加了三个这样对 象，valHooks，attrHooks, propHooks，分别对应val，attr与prop这个三个方法。prop是新增的，表示jQuery决定区分属性与特性的决心，但IE6/7还是 无法区分它们，因此attr基本上涵盖了prop的功能。

我们看一下它们各自的运用吧！

// jQuery.style 方法

      if ( value !== undefined ) {

        //=================略==============

        // If a hook was provided, use that value, otherwise just set the specified value

        if ( !hooks || !("set" in hooks) || (value = hooks.set( elem, value )) !== undefined ) {

          // Wrapped to prevent IE from throwing errors when 'invalid' values are provided

          // Fixes bug #5509

          try {

            style[ name ] = value;

          } catch(e) {}

        }

      } else {

        // If a hook was provided get the non-computed value from there

        if ( hooks && "get" in hooks && (ret = hooks.get( elem, false, extra )) !== undefined ) {

          return ret;

        }

        // Otherwise just get the value from the style object

        return style[ name ];

      }

// jQuery.fn.val 方法

      if ( !arguments.length ) {

        if ( elem ) {

          hooks = jQuery.valHooks[ elem.nodeName.toLowerCase() ] || jQuery.valHooks[ elem.type ];

          if ( hooks && "get" in hooks && (ret = hooks.get( elem, "value" )) !== undefined ) {

            return ret;

          }

          return (elem.value || "").replace(rreturn, "");

        }

        return undefined;

      }

     //===============略============

      hooks = jQuery.valHooks[ this.nodeName.toLowerCase() ] || jQuery.valHooks[ this.type ];

      // If set returns undefined, fall back to normal setting

      if ( !hooks || ("set" in hooks && hooks.set( this, val, "value" ) === undefined) ) {

        this.value = val;

      }

// jQuery.attr 方法

     hooks = jQuery.attrHooks[ name ] || ( jQuery.nodeName( elem, "form" ) && formHook );

      if ( value !== undefined ) {

        if ( value === null || (value === false && !rspecial.test( name )) ) {

          jQuery.removeAttr( elem, name );

          return undefined;

        } else if ( hooks && "set" in hooks && notxml && (ret = hooks.set( elem, value, name )) !== undefined ) {

          return ret;

        } else {

          // Set boolean attributes to the same name

          if ( value === true && !rspecial.test( name ) ) {

            value = name;

          }

          elem.setAttribute( name, "" + value );

          return value;

        }

      } else {

        if ( hooks && "get" in hooks && notxml ) {

          return hooks.get( elem, name );

        } else {

          ret = elem.getAttribute( name );

          // Non-existent attributes return null, we normalize to undefined

          return ret === null ? undefined : ret;

        }

      }

// jQuery.prop 方法

           hooks = jQuery.propHooks[ name ];

        if ( value !== undefined ) {

            if ( hooks && "set" in hooks && (ret = hooks.set( elem, value, name )) !== undefined ) {

                return ret;

            } else {

                return (elem[ name ] = value);

            }

        } else {

            if ( hooks && "get" in hooks && (ret = hooks.get( elem, name )) !== undefined ) {

                return ret;

            } else {

                return elem[ name ];

            }

        }

//jQuery.event.add

      if ( !special.setup || special.setup.call( elem, data, namespaces, eventHandle ) === false ) {

        // Bind the global event handler to the element

        if ( elem.addEventListener ) {

          elem.addEventListener( type, eventHandle, false );

        } else if ( elem.attachEvent ) {

          elem.attachEvent( "on" + type, eventHandle );

        }

      }

//jQuery.event.remove

      if ( !special.teardown || special.teardown.call( elem, namespaces ) === false ) {

        jQuery.removeEvent( elem, type, elemData.handle );

      }

可以发现还是很有章法的。这些适配器就是用来处理一些特殊的属性，样式或事件。而这些属性，样式或事件，我们可以通过浏览器的特征嗅探，把相应的解 决方法添加到适配器中。有了这些适配器，jQuery就可以省去许多if else 判定，当正式版发布时，又可以高兴地宣布这几个方法快了多少百分比了！