组合数组、循环和 if 语句

Question

我试图了解如何组合应用数组、循环和 if 语句。我已经创建了一个工作日数组，我想指定在特定的一天应该分配特定的锻炼。我还想打印出分配的日期和练习。正如您将在下面的代码中看到的那样，使用weekday.push() 方法分配隔日游泳或重量训练，根本不添加瑜伽并创建 14 个值。你能否建议如何处理这个问题。谢谢！

var weekday = ['Sun', 'Mon', 'Tues', 'Wed', 'Thur', 'Fri', 'Sat'];
var workOut = [];

function myExercise() {
  for (var i = 0; i < weekday.length; i++) {
    if (weekday == 'Wed' || 'Mon' || 'Fri') {
      workOut.push('Swimming');
    }
    if (weekday == 'Tue' || 'Thur' || 'Sat') {
      workOut.push('weight training');
    } else {
      workOut.push('Yoga' + 'or' + 'power walking');
    }
  }
}

myExercise();
console.log(workOut);

Answer 1

不幸的是，您不能像在 if 子句中尝试的那样使用快捷方式。你也忘记了迭代器[i]。除了正常的

if (weekday[i] == 'Wed' || weekday[i] == 'Mon' ||  weekday[i] == 'Fri')

您也可以使用以下形式：

if ( ['Wed','Mon','Fri'].includes(weekday[i]))

如果您想支持 IE（不支持 includes），您可以使用 indexOf。

当您想要检查大量值时，这很方便。总之，你可以这样写：

注意，我还将您的第二个 if 更改为 else if（这是 14 个条目的原因）并使用了 Array.prototype.map 函数。此外，操作不属于您的范围的对象是一个坏习惯（锻炼在全局范围内，但被myExercise 函数操作）。最好返回想要的结果，然后做一个简单的赋值。

var weekday = ['Sun', 'Mon', 'Tue', 'Wed', 'Thur', 'Fri', 'Sat'];
var workOut = [];

function myExercise() {

  return weekday.map(function(day){
      var workout;
      if (['Mon','Wed','Fri'].includes(day)){
        workout = "Swimming";
      } else if (['Tue','Thur','Sat'].includes(day)){
        workout = "Weight training";
      } else {
        workout = 'Yoga or power walking';
      }
      return workout;
  });
}

workOut = myExercise();
console.log(workOut);

Answer 2

修改了你的代码，有拼写错误和条件重叠

var weekday = ['Sun', 'Mon', 'Tues', 'Wed', 'Thur', 'Fri', 'Sat'];
var workOut = [];

function myExercise() {
  for (var i = 0; i < weekday.length; i++) {
  console.log(weekday[i] )
    if (weekday[i] == 'Wed' || weekday[i] == 'Mon' || weekday[i] == 'Fri') {
      workOut.push('Swimming');
    }
    else{
    if (weekday[i] == 'Tues' || weekday[i] == 'Thur' || weekday[i] == 'Sat') {
      workOut.push('weight training');
    } else {
      workOut.push('Yoga' + 'or' + 'power walking');
    }
    }
  }
}

myExercise();
console.log(workOut);
VM280:18 

Answer 3

var weekdays = ['Sun', 'Mon', 'Tues', 'Wed', 'Thur', 'Fri', 'Sat'];
var workouts = weekdays.map(day => {
  switch (day) {
    case 'Wed':
    case 'Mon':
    case 'Fri':
      return 'Swimming';
      break;
    case 'Tues':
    case 'Thur':
    case 'Sat':
      return 'weight training';
      break;
    default:
      return 'Yoga or power walking';
      break;
  }
});

console.log(workouts);

Answer 4

之前的答案中已经有 switch 语句，但我也包括了这个。它可能不是 DRY，但对于初学者来说更容易理解：

var weekday = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
var workOut = [];

function myExercise() {    
    for (var i = 0; i < weekday.length; i++) {
        switch(weekday[i]) {
            case 'Sun':
                workOut.push('Yoga' + 'or' + 'power walking');
                break;
            case 'Mon':
                workOut.push('Swimming');
                break;
            case 'Tue':
                workOut.push('weight training');
                break;
            case 'Wed':
                workOut.push('Swimming');
                break;
            case 'Thu':
                workOut.push('weight training');
                break;
            case 'Fri':
                workOut.push('Swimming');
                break;
            case 'Sat':
                workOut.push('weight training');
                break;
                default:
                workOut.push('Sleep!!');
        }
    }
}

myExercise();
console.log(workOut);