if ( state === 'jump' ){
   if ( currState === 'attack' || currState === 'defense' ){
     return false;
   }
}else if ( state === 'wait' ){
   if ( currState === 'attack' || currState === 'defense' ){
     return true;
   }
}

var StateManager = function(){
  var currState = 'wait';
  var states = {
    jump: function( state ){
    },
    wait: function( state ){
    },
    attack: function( state ){
    },
    crouch: function( state ){
    },
    defense: function( state ){
      if ( currState === 'jump'  ){
          return false;  //不成功，跳跃的时候不能防御
      }
    //do something;     //防御的真正逻辑代码, 为了防止状态类的代码过多, 应该把这些逻辑继续扔给真正的fight类来执行.
    currState = 'defense'; //  切换状态
    }
  }
  var changeState = function( state ){
    states[ state ] && states[ state ]();
  }
  return {
      changeState  : changeState
  }
}
var stateManager = StateManager();
stateManager.changeState( 'defense' );