这个字符计数代码的逻辑错误是什么？

Question

对于为什么这不能按预期工作，我真的处于停滞状态。它应该输出字母 s 在单词 Mississipi 中出现次数的数字 4。我是 javascript 新手，所以任何帮助将不胜感激。利亚姆function countCharacters(target, input) { //Defining of the function, the parameters are target and input  var count = 0; //set count to 0 before the for loop  for (var i = 0; i < input.length; i = i + 1) { //the for loop that goes through each index of the input string    if (input.indexOf(i) == target) { //if a character in the string matches the target character      count = count + 1; //count adds 1 to its value    }  }  console.log(count); //When it breaks out of the loop, the amount of times the target was matched will be printed  return target, input; //return two parameters}console.log(countCharacters("s", "Mississippi"));

Answer 1

您不需要Array.indexOf()找到当前角色。由于i是当前字符的索引，用它从字符串中取出当前字符，并与目标进行比较。最后返回count。

注意：returnJS 中的语句不能返回两个项。如果您使用逗号分隔的列表 -target, input例如 - 最后一项将被返回。

function countCharacters(target, input) {

  var count = 0;

  

  for (var i = 0; i < input.length; i = i + 1) {

    if (input[i] === target) { //if a character in the string matches the target character

      count = count + 1;

    }

  }

  return count;

}

console.log(countCharacters("s", "Mississippi"));

Answer 2

在这里，您正在与索引和目标进行比较。你应该得到当前字符然后比较。正如我在下面所做的那样，它可能会帮助您...

function countCharacters(target, input) { //Defining of the function, the parameters are target and input

  var count = 0; //set count to 0 before the for loop

  for (var i = 0; i < input.length; i = i + 1) { //the for loop that goes through each index of the input string

    if (input[i] == target) { //if a character in the string matches the target character

      count = count + 1; //count adds 1 to its value

    }

  }

  console.log(count); //When it breaks out of the loop, the amount of times the target was matched will be printed

  return target, input; //return two parameters

}

console.log(countCharacters("s", "Mississippi"));

Answer 3

事情是这样的：您尝试通过 indexOf() 访问字母 - 最好通过索引访问它，而且函数必须只返回一件事，而您的则返回两件事

function countCharacters(target, input) { 

  let count = 0; 

  for (let i = 0; i < input.length; i++) { 

    if (input[i] === target) { 

      count++; 

    }

  } 

  return count;

}

console.log(countCharacters("s", "Mississippi"));