javascript - 计算 Javascript 中所有字符串字符中某个字符在字符串中使用的次数

Question

编写一个名为 strLetterCount 的函数，它接受一个字符串并返回一个新字符串，其中每个字符后跟该字符在字符串中出现的次数。

例如:

strLetterCount("taco"); // "t1a1c1o1"

我的代码在这里离目标很远，但这就是我得到的......

我将继续查找每个字母，然后尝试返回正确的字符串。我知道这不是一个好方法。有什么帮助吗？

function strLetterCount(str) {

  var countA = 0;
  var countB = 0;
  var countC = 0;
  var countD = 0;
  var countE = 0;
  var countF = 0;
  var countG = 0;
  var countH = 0;
  var countI = 0;
  var countJ = 0;
  var countK = 0;
  var countL = 0;
  var countM = 0;
  var countN = 0;
  var countO = 0;
  var countP = 0;
  var countQ = 0;
  var countR = 0;
  var countS = 0;
  var countT = 0;
  var countU = 0;
  var countV = 0;
  var countW = 0;
  var countX = 0;
  var countY = 0;
  var countZ = 0;

  for (var i = 0; i < str.length; i++);
  if (str[i] === 'a') {
    countA++;
  }
  for (var i = 0; i < str.length; i++);
  if (str[i] === 'b') {
    countB++;
  }
  for (var i = 0; i < str.length; i++);
  if (str[i] === 'c') {
    countC++;
  }
  return {"a":countA,"b":countB,"c":countC}
}

console.log(
  strLetterCount("The quick brown fox jumps over the lazy dog")
)  

Answer 1

只需循环遍历字符串的每个字符，并将它们计入一个对象中。

一个简单的解决方案是:

let str = "The quick brown fox jumps over the lazy dog";

const count = string => {
  const characters = {};
  for (let character of string) {
    characters[character] = characters[character] + 1 || 1;
  }
  return characters;
}

console.log(count(str));

您可以将结果用作:

let result = count(str);
console.log(result["o"]); // 4

更新

如果您需要字符串输出，一种选择是使用第二个循环来写出结果:

let str = "The quick brown fox jumps over the lazy dog";

const count = string => {
  const characters = {};
  let str = "";
  
  for (let character of string) {
    characters[character] = characters[character] + 1 || 1;
  }
  for (let key in characters) {
    str += `${key}${characters[key]}`
  }
  return str;
}

console.log(count(str));

或者，如果您不关心格式:

return JSON.stringify(characters);