要计算字符串中每个字符出现的次数，可以使用for循环遍历字符串，并将每个字符作为键添加到对象中，值为它出现的次数。下面是一个示例：

// create an empty object to store the character counts
var charCounts = {};

// get the string from the array
var str = ["academy"][0];

// iterate through the string and count the occurrences of each character
for (var i = 0; i < str.length; i++) {
  var char = str[i];
  if (charCounts[char] === undefined) {
    // if the character has not been encountered before, set its count to 1
    charCounts[char] = 1;
  } else {
    // if the character has been encountered before, increment its count by 1
    charCounts[char]++;
  }
}

// print the character counts
for (var char in charCounts) {
  console.log(char + ": " + charCounts[char]);
}

这里有一个简洁的方法。[...new Set(word.split(''))]创建一个字母数组，忽略所有重复的字母。.map从该数组中取出每个字母，并通过长度检查器对其进行检查。({ [m]: word.split(m).length - 1 })将该字母设置为object key，word.split(m).length - 1是一种快速确定该字母出现次数的方法。

const countLetters = word => (
  [...new Set(word.split(''))].map(m => ({
    [m]: word.split(m).length - 1
  })))

console.log(countLetters("academy"))

你也可以用正则表达式来检查出现的字符串。在这里我做了一个方法来检查字符串中的字符。希望它能有所帮助。

word: string = 'abcdefghijklkmnopqrstuvwxyzgg';
charsArrayWithCount = {};
CheckWordCount(): void {
    for(var i = 0;i < this.word.length; i++){
        if(this.charsArrayWithCount[this.word[i]] === undefined){
            this.charsArrayWithCount[this.word[i]] = this.charCount(this.word, this.word[i]);
        }
    }
    console.log(this.charsArrayWithCount);
}
charCount(string, char) {
    let expression = new RegExp(char, "g");
    return string.match(expression).length;
}