Question

我有一个带有else块的if语句，它们都在for循环中。当我执行它时，它总是返回if语句和else语句中的值。当if语句为false时，它是否只能转到else块？

＆＃13;

<!DOCTYPE html>
<html>
<body>

<p>Click the button to begin</p>

<button onclick="myFunction()">Try it</button>

<script>

const moodList = {
    sad: {
        quotes: ['this is a sad quote',
                 'this is a sad quote number 2',
                 'this is a sad quote number 3'
                ]
    },
    happy: {
        quotes: ['this is a happy quote',
                 'this is a happy quote number 2',
                 'this is a happy quote number 3'
                ]
    }
}

function myFunction() {

  let moodInput = prompt('Enter a feeling');

  for (var key in moodList) {
    if (moodInput.includes(key)) {
      console.log('you got a result!');
    } else {
      console.log('nothing');
    }
  }
}
</script>

</body>
</html>

＆＃13;

Answer 1

您可以检查输入的值是否是对象上的键，而不是在对象上创建循环：

if (moodList[moodInput]) {
  console.log('you got a result!');
} else {
  console.log('nothing');
}

更新代码：

const moodList = {
  sad: {
    quotes: ['this is a sad quote',
      'this is a sad quote number 2',
      'this is a sad quote number 3'
    ]
  },
  happy: {
    quotes: ['this is a happy quote',
      'this is a happy quote number 2',
      'this is a happy quote number 3'
    ]
  }
}

function myFunction() {
  let moodInput = prompt('Enter a feeling');
  if (moodList[moodInput]) {
    console.log('you got a result!');
  } else {
    console.log('nothing');
  }
}

<p>Click the button to begin</p>

<button onclick="myFunction()">Try it</button>

Answer 2

您可以使用密钥并检查密钥是否在in operator的对象中。

＆＃13;

const moodList = {
    sad: {
        quotes: ['this is a sad quote',
                 'this is a sad quote number 2',
                 'this is a sad quote number 3'
                ]
    },
    happy: {
        quotes: ['this is a happy quote',
                 'this is a happy quote number 2',
                 'this is a happy quote number 3'
                ]
    }
};

function myFunction() {
    let moodInput = prompt('Enter a feeling');

    if (moodInput in moodList) {
        console.log('you got a result!');
    } else {
        console.log('nothing');
    }
}

＆＃13;

<p>Click the button to begin</p>
<button onclick="myFunction()">Try it</button>

＆＃13;

Javascript For..In循环执行if和else语句

2 个答案: