如何在其他函数中使用函数表达式值？答案

【问题标题】：How to use function expression values in other functions?如何在其他函数中使用函数表达式值？
【发布时间】：2020-05-30 21:50:06
【问题描述】：

我正在学习 Javascript，我做了一个石头、剪刀、纸的项目。我已经使它与示例代码一起工作，但现在我想使用函数表达式在其他函数中使用它的值。当我加载代码时，它给了我未定义的，我不知道为什么。我分配所有值。这是我的代码。

const userChoice = userInput => {
  //userInput = userInput.toLowerCase();
  if (userInput === 'rock' || userInput === 'scissors' || userInput === 'paper' || userInput === 'bomb') {
    return userInput;
  } else {
    console.log('Error!');
  }
}

//console.log(getUserChoice('Fork'));

const computerChoice = function() {
  const randomNumber = Math.floor(Math.random() * 3);
  switch (randomNumber) {
    case 0:
      return 'rock';
    case 1:
      return 'paper';
    case 2:
      return 'scissors'
  }
};
//console.log(getComputerChoice());

function determineWinner(userChoice, computerChoice) {
  console.log()
  if (userChoice === computerChoice) {
    return 'The game is a tie!'
  }
  if (userChoice === 'rock') {
    if (computerChoice === 'paper') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'scissors') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'paper') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'bomb') {
    return 'You won!';

  }
}

const playGame = () => {

  console.log('You threw: ' + userChoice('rock'));
  console.log('The computer threw: ' + computerChoice());
  console.log(determineWinner(userChoice, computerChoice));
}
playGame();

请帮帮我。

【问题讨论】：

所以澄清一下，computerChoice = function() 与拥有类似函数 getComputerChoice() 的函数然后分配到类似 let computerChoice = getComputerChoice() 的变量不同？为什么？ – Andres Pelaez 15 分钟前删除

标签： javascript function function-expression

【解决方案1】：

你将函数userChoice作为参数传递，你应该将调用函数userChoice的结果存储起来，并将结果作为参数传递给函数determineWinner

const userChoice = userInput => {
  //userInput = userInput.toLowerCase();
  if (userInput === 'rock' || userInput === 'scissors' || userInput === 'paper' || userInput === 'bomb') {
    return userInput;
  } else {
    console.log('Error!');
  }
}

//console.log(getUserChoice('Fork'));

const computerChoice = function() {
  const randomNumber = Math.floor(Math.random() * 3);
  switch (randomNumber) {
    case 0:
      return 'rock';
    case 1:
      return 'paper';
    case 2:
      return 'scissors'
  }
};
//console.log(getComputerChoice());

function determineWinner(userChoice, computerChoice) {
  if (userChoice === computerChoice) {
    return 'The game is a tie!'
  }
  if (userChoice === 'rock') {
    if (computerChoice === 'paper') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'scissors') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'paper') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'bomb') {
    return 'You won!';

  }
}

const playGame = () => {
  
  let uc = userChoice('rock');
  
  console.log('You threw: ' + uc);
  console.log('The computer threw: ' + computerChoice());
  console.log(determineWinner(uc, computerChoice));
}
playGame();

【讨论】：

【解决方案2】：

您应该将userChoice 和computerChoice 的输出分配给变量，然后再将它们传递给determineWinner

const userChoice = userInput => {
  //userInput = userInput.toLowerCase();
  if (userInput === 'rock' || userInput === 'scissors' || userInput === 'paper' || userInput === 'bomb') {
    return userInput;
  } else {
    console.log('Error!');
  }
}

//console.log(getUserChoice('Fork'));

const computerChoice = function() {
  const randomNumber = Math.floor(Math.random() * 3);
  switch (randomNumber) {
    case 0:
      return 'rock';
    case 1:
      return 'paper';
    case 2:
      return 'scissors'
  }
};
//console.log(getComputerChoice());

function determineWinner(userChoice, computerChoice) {
  console.log()
  if (userChoice === computerChoice) {
    return 'The game is a tie!'
  }
  if (userChoice === 'rock') {
    if (computerChoice === 'paper') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'scissors') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'paper') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'bomb') {
    return 'You won!';

  }
}

const playGame = () => {
  const userChose = userChoice('rock')
  const computerChose = computerChoice()
  console.log('You threw: ' + userChose);
  console.log('The computer threw: ' + computerChose);
  console.log(determineWinner(userChose, computerChose));
}
playGame();

【讨论】：

所以澄清一下，computerChoice = function() 与拥有类似函数 getComputerChoice() 的函数然后分配到类似 let computerChoice = getComputerChoice() 的变量不同？为什么？
computerChoice = function() {...} 是我们声明函数的部分。与拥有getComputerChoice之类的函数并声明变量let computerChoiceVariable = getComputerChoice()是不一样的

【解决方案3】：

试试这个

const userChoice = userInput => {
  //userInput = userInput.toLowerCase();
  if (userInput === 'rock' || userInput === 'scissors' || userInput === 'paper' || userInput === 'bomb') {
    return userInput;
  } else {
    console.log('Error!');
  }
}

//console.log(getUserChoice('Fork'));

const computerChoice = function() {
  const randomNumber = Math.floor(Math.random() * 3);
  switch (randomNumber) {
    case 0:
      return 'rock';
    case 1:
      return 'paper';
    case 2:
      return 'scissors'
  }
};
//console.log(getComputerChoice());

function determineWinner(userChoice, computerChoice) {
  console.log()
  if (userChoice === computerChoice) {
    return 'The game is a tie!'
  }
  if (userChoice === 'rock') {
    if (computerChoice === 'paper') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'scissors') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'paper') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'bomb') {
    return 'You won!';

  }
}

const playGame = () => {

  console.log('You threw: ' + userChoice('rock'));
  console.log('The computer threw: ' + computerChoice());
  console.log(determineWinner(userChoice('rock'), computerChoice()));
}
playGame();

【讨论】：

【解决方案4】：

只是一些错误。您需要将值存储到变量中。

const userChoice = userInput => {
  //userInput = userInput.toLowerCase();
  if (userInput === 'rock' || userInput === 'scissors' || userInput === 'paper' || userInput === 'bomb') {
    return userInput;
  } else {
    console.log('Error!');
  }
}

//console.log(getUserChoice('Fork'));

const computerChoice = function() {
  const randomNumber = Math.floor(Math.random() * 3);
  switch (randomNumber) {
    case 0:
      return 'rock';
    case 1:
      return 'paper';
    case 2:
      return 'scissors'
  }
};
//console.log(getComputerChoice());

function determineWinner(userChoice, computerChoice) {
  console.log()
  if (userChoice === computerChoice) {
    return 'The game is a tie!'
  }
  if (userChoice === 'rock') {
    if (computerChoice === 'paper') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'scissors') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'paper') {
    if (computerChoice === 'rock') {
      return 'The computer won!';
    } else {
      return 'You won!'
    }
  }
  if (userChoice === 'bomb') {
    return 'You won!';

  }
}

const playGame = () => {
  const threw = {
      computer: null,
      user: null
  }
  threw.user = userChoice("rock")
  threw.computer = computerChoice()
  
  console.log('You threw: ' + threw.user);
  console.log('The computer threw: ' + threw.computer);
  console.log(determineWinner(userChoice(threw.user), threw.computer));
}
playGame();

【讨论】：