JavaScript:无法突破for of循环

Question

我正在研究由一个对象/类表示的火星漫游者的模拟(链接到示例)。你应该能够根据火星的地形给它输入方向，并以JavaScript物体的形式得到一个输出，这将更新你的漫游者是如何在地形中前进的。

我已经算出了其他的条件，但我的问题是，当漫游者撞上一座山或裂缝时，我的问题是要想出一个逻辑。

这些是与基于地形的漫游对象/类一起使用的数据类型。

const TERRAIN_TYPES = {
  'P': {
    obstacle: false,
    description: 'plains'
  },
  'M': {
    obstacle: true,
    description: 'mountains'
  },
  'C': {
    obstacle: true,
    description: 'crevasse'
  }
};

const STATUS_CODES = ['OK', 'OBSTACLE', 'INVALID_COMMAND'];

// top left corner is (X:0, Y:0)
// bottom right is (X:4, Y:4)
const WORLD = [
  ['P', 'P', 'P', 'C', 'P'],
  ['P', 'M', 'P', 'C', 'P'],
  ['P', 'M', 'P', 'C', 'P'],
  ['P', 'M', 'P', 'P', 'P'],
  ['P', 'M', 'P', 'P', 'P']
];

const DIRECTIONS = ['N', 'S', 'E', 'W'];
const COMMANDS = ['L', 'R', 'F', 'B'];

这是我创建的对象/类enter code here。

class Rover {

  constructor(location, direction) {
    this.location = location
    this.direction = direction
    this.commands = []
  }

  positionPossible(value) {
    return TERRAIN_TYPES[value].obstacle
  }
 
  command(commands) {
    this.commands = [...this.commands, ...commands];
    if (COMMANDS.indexOf(this.commands[0]) == -1) {
      return {
        status: STATUS_CODES[2],
        loc: this.location,
        dir: this.direction
      }
    }
    return this.roverController()
  }

  roverController() {
    const TURN_LEFT_CMD = COMMANDS[0];
    const TURN_RIGHT_CMD = COMMANDS[1];
    const MOVE_FORWARD_CMD = COMMANDS[2];
    const MOVE_BACKWARD_CMD = COMMANDS[COMMANDS.length - 1]

    const commands = this.commands
    let res = {
      status: null,
      loc: this.location,
      dir: this.direction
    }

    if (DIRECTIONS.indexOf(this.direction) !== -1) {
      
      for (let element of commands) {
        if (element === TURN_LEFT_CMD) {
          this.direction = DIRECTIONS[DIRECTIONS.length - 1];
          res = {
            ...res,
            ...{
              status: STATUS_CODES[0],
              loc: this.location,
              dir: this.direction
            }
          }
        }
        if (element === TURN_RIGHT_CMD) {
          this.direction = DIRECTIONS[DIRECTIONS.length - 2];
          res = {
            ...res,
            ...{
              status: STATUS_CODES[0],
              loc: this.location,
              dir: this.direction
            }
          }
        }
        if (element === MOVE_FORWARD_CMD) {
          if (this.positionPossible(WORLD[this.location[0]][this.location[1]]) === false) {
            this.location[1] = this.location[1] = this.location[1] - 1;
             res = {
              ...res,
              ...{
                status: STATUS_CODES[0],
                loc: this.location,
                dir: this.direction

              }
            }
          } else {
           if (this.positionPossible(WORLD[this.location[0]][this.location[1]]) === true) {
          
            this.direction = (commands[commands.indexOf(element - 1)] === 'L') ? 'E' : 'W'
            this.location[1] = this.location[1] = this.location[1] + 1;            
            return res = {
              ...res,
              ...{
                status: STATUS_CODES[1],
                loc: this.location,
                dir: this.direction

              }
            }
  break
          }
        }
        }
        if (element === MOVE_BACKWARD_CMD && !this.positionPossible(WORLD[this.location[0]][this.location[1]])) {
          this.location[1] = this.location[1] = this.location[1] + 1;
          res = {
            ...res,
            ...{
              status: STATUS_CODES[0],
              loc: this.location,
            }
          }
        }

      }
      return res
    }
  }
}

您会注意到，我创建了一个函数roverController()，它包含一些特定数据条件的枚举，以及一个for-of循环，它正在遍历创建的命令并向后吐回一个响应对象，以获得反馈。

let res = {
   status: null,
   loc: this.location,
   dir: this.direction
 }

当它命中条件时，我用不断变化的状态更新响应对象，

这就是月球车撞到无法通过的地形时应该给我的错误：

  if (this.positionPossible(WORLD[this.location[0]][this.location[1]]) === true) {
              
                this.direction = (commands[commands.indexOf(element - 1)] === 'L') ? 'E' : 'W'
                this.location[1] = this.location[1] = this.location[1] + 1;            
                return res = {
                  ...res,
                  ...{
                    status: STATUS_CODES[1],
                    loc: this.location,
                    dir: this.direction
    
                  }
                }
      break
              }
            }

我认为返回(或中断)语句会将一个函数踢出并返回status对象，但它没有；

任何帮助都将不胜感激!！

Answer 1

break终止执行它的循环。请参阅https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/break

return后面跟着一个值退出一个函数，将值返回到最初调用该函数的语句。请参阅https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/return

就个人而言，为了提高可读性，我喜欢任何return语句都是函数中的最后一条语句。因此，一个好的结构是：

...

  for (...) {
    if (whatever) {
    returnValue = ...
    break; // loop exits regardless of conditional;
    }

  } // end for loop;

return returnValue; // returnValue set in loop before break;

} // end function