如何在中断之前遍历此 for 循环中的所有城市?现在它只是迭代一个

How do I iterate through all the cities inside this for loop before breaking? Right now it's only iterating through one

本文关键字：迭代 一个 城市 遍历 中断 for 循环      更新时间：2023-09-26

我知道我的第一个中断语句在错误的地方，只是想说明我试图用这个练习题做什么。 如何让 if 语句遍历 for 循环内数组中的所有城市？ 它只是遍历第一个（我理解 - 它迭代一次然后中断）。 目标是遍历所有城市，然后在返回数组中的任何城市后中断。 

function cityInput(city) {
  var cityToCheck = prompt("Enter your city");
  cityToCheck = cityToCheck.toLowerCase();
  var cleanestCities = ["cheyenne", "santa fe", "tucson", "great falls", "honolulu"];
  for (var i = 0; i <= 4; i++) {
    if (cityToCheck === cleanestCities[i]) {
      alert("It's one of the cleanest cities");
      break;
    } else {
      alert("city not listed");
      break;
    }
  }
};
cityInput();

可以使用警报的默认值，并且仅在找到城市时中断。

function cityInput(city) {
    var cityToCheck = prompt("Enter your city"),
        cleanestCities = ["cheyenne", "santa fe", "tucson", "great falls", "honolulu"],
        msg = "city not listed";
    cityToCheck = cityToCheck.toLowerCase();
    for (var i = 0; i <= 4; i++) {
        if (cityToCheck === cleanestCities[i]) {
            msg = "It's one of the cleanest cities";
            break;
        }
    }
    alert(msg);
};
cityInput();

} else {
  alert("city not listed");
  break;
}

如果数组中的当前城市不是您要查找的城市，则正在中断。但是，下一个城市可能是您正在寻找的城市。在得出此结论之前，您应该做的是查看整个数组。例如，你可以做

var cleanestCities = ["cheyenne", "santa fe", "tucson", "great falls", "honolulu"];
var foundCity = false;
for (var i = 0; i <= 4; i++) {
    if (cityToCheck === cleanestCities[i]) {
        foundCity = true;
        break;
    }
}
if (foundCity) {
    alert("It's one of the cleanest cities");
} else {
    alert("city not listed");
}

实际上，您可以使用Array.indexOf函数并像这样编写整个函数

if (cleanestCities.indexOf(cityToCheck) !== -1) {
    alert("It's one of the cleanest cities");
} else {
    alert("city not listed");
}

或者Array.prototype.some，像这样

if (cleanestCities.some(function(currentCity) {
    return currentCity === cityToCheck;
})) {
    alert("It's one of the cleanest cities");
} else {
    alert("city not listed");
}

使用 ES6 的箭头函数，您可以编写相同的

if (cleanestCities.some((currentCity) => currentCity === cityToCheck)) {
    alert("It's one of the cleanest cities");
} else {
    alert("city not listed");
}

你不需要遍历所有城市，我相信这是矫枉过正。你可以只使用Array.indexOf并实现它，如下所示...

function cityInput(city) {
    var cityToCheck = prompt("Enter your city");
    var cleanestCities = ["cheyenne", "santa fe", "tucson", "great falls", "honolulu"];
    cityToCheck = cityToCheck.toLowerCase();
    if (cleanestCities.indexOf(cityToCheck) >= 0) {
        alert("It's one of the cleanest cities");
    } else {
        alert("city not listed");
    }
}
cityInput();

function cityInput() {
  var cityToCheck = prompt("Enter your city");
  cityToCheck = cityToCheck.toLowerCase();
  var cleanestCities = ["cheyenne", "santa fe", "tucson", "great falls", "honolulu"];
  for (var i = 0; i <= 4; i++) {
    if (cityToCheck === cleanestCities[i]) {
      alert("It's one of the cleanest cities");
      return;
     }
   }
   alert("city not listed");
};

这应该做到

尝试该方法

localeCompare()

而不是

=== if 语句中的运算符。

应该看起来像这样：

if (cityToCheck.localeCompare(cleanestCities[i]))
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