Question

我对此代码有疑问：

var buyerChoice = prompt("Enter a either apple, orange, or banana:", "");        

var fruits = new Array ("apple", "orange", "banana");

for(i=0; i < fruits.length; i++) {
    if(buyerChoice === fruits[i]) {
        document.write(buyerChoice);
    } else if (buyerChoice !== fruits[i]){
        document.write("Sorry, " +buyerChoice+ " is out of season.");
        break;
    }
}

我认为问题出在else-if语句中，因为每次输入我的变量中存在的项目时，它都会返回//appleSorry, apple is out of season，从而满足这两个条件。

我很难过。我想底线是如何有效地匹配从提示符到数组的字符串，测试每个项目以及如果提示字符串不存在，如何解析数组。

Answer 1

在第一次迭代中，输入的水果要么等于或不等于“apple”。但如果它不是第一次迭代的“苹果”（但例如“橙色”），那么这并不意味着“橙色”根本不可用。

你应该跟踪你是否匹配任何东西（通过使用变量），并且只有当循环之后没有匹配时，输入的水果确实不可用。

Answer 2

你的for循环根本不符合逻辑。因此items如果未定义则不会工作。

这是一个可能的解决方案

var outofseason = true;
for(i=0; i < fruits.length; i++) {
    if(buyerChoice === fruits[i]) {
        outofseason = false;
        break;
    }
}

if ( outofseason ) {
    document.write("Sorry, " +buyerChoice+ " is out of season.");
}
else {
    document.write(buyerChoice);
}

Answer 3

// let the fruits be a global var instead of recreating it every time you call the function below
var fruits = ["apple", "orange", "banana"];

function askBuyerForFruit() {
  var buyerChoice = prompt("Enter a either apple, orange, or banana:", "");

  for (var i = 0; i < fruits.length; i++) {
    if (fruits[i] === buyerChoice) {
      document.write(buyerChoice);
      // get out of the function if found;
      return;
    }
  }

  // fallback if no matching fruit found
  document.write("Sorry, " +buyerChoice+ " is out of season.");
}

希望这会有所帮助：）

Answer 4

不是100％确定for循环尝试完成的内容，但您可以使用indexOf

var buyerChoice = prompt("Enter a either apple, orange, or banana:", "");
var fruits = new Array ("apple", "orange", "banana");

var matchedIndex = fruits.indexOf(buyerChoice);

if (matchedIndex < 0) { //did not match
    document.write("Sorry, " +buyerChoice+ " is out of season.");
} else {
    document.write(buyerChoice)
}

Answer 5

将项目[i]更改为fruit [i]这将解决您的问题

Answer 6

var buyerChoice = prompt("Enter a either apple, orange, or banana:", "");        

var fruits = ["apple", "orange", "banana"];

var outOfSeason = false;
for(fruit in fruits) {
    if(buyerChoice === fruits[fruit]) {
        matched = true;
        break;
    }
}

if(! outOfSeason){
   document.write(buyerChoice);
}
else{
   document.write("Sorry, " +buyerChoice+ " is out of season.");
}

将字符串与数组匹配

6 个答案: