[jQuery] val 메소드 getter, setter 구별법

결국 arguments의 length 속성을 이용한다.

  val: function( value ) {
    var hooks, ret, isFunction,
      elem = this[0];

    if ( !arguments.length ) {
      if ( elem ) {
        hooks = jQuery.valHooks[ elem.type ] || jQuery.valHooks[ elem.nodeName.toLowerCase() ];

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

        ret = elem.value;

        return typeof ret === "string" ?
          // handle most common string cases
          ret.replace(rreturn, "") :
          // handle cases where value is null/undef or number
          ret == null ? "" : ret;
      }

      return;
    }

    isFunction = jQuery.isFunction( value );

    return this.each(function( i ) {
      var self = jQuery(this), val;

      if ( this.nodeType !== 1 ) {
        return;
      }

      if ( isFunction ) {
        val = value.call( this, i, self.val() );
      } else {
        val = value;
      }

      // Treat null/undefined as ""; convert numbers to string
      if ( val == null ) {
        val = "";
      } else if ( typeof val === "number" ) {
        val += "";
      } else if ( jQuery.isArray( val ) ) {
        val = jQuery.map(val, function ( value ) {
          return value == null ? "" : value + "";
        });
      }

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

      // If set returns undefined, fall back to normal setting
      if ( !hooks || !("set" in hooks) || hooks.set( this, val, "value" ) === undefined ) {
        this.value = val;
      }
    });
  }