如何计算特定字符在字符串中的出现次数 [英] How to count the number of times specific characters are in a string

问题描述

我正在尝试创建一个函数，以查看数组中的任何字符是否在字符串中，如果是，则多少个字符.

I am trying to create a function that looks to see if any of the characters in an array are in a string, and if so, how many.

我尝试计算每种模式，但是太多了.我尝试使用Python中"in"运算符的替代方法，但效果不佳

I have tried to calculate every pattern, but there is too much. I tried using the alternative to the "in" operator from Python, but that didn't work out as well

function calc_fit(element) {
  var fitness_let = ["e", "l", "m", "n", "t"]

  }
}

element 是字符串，而Fitness_let数组是我需要检查的东西数组，以查看它们是否在字符串中，如果存在，则检查多少.

The element is the string, and the fitness_let array is the array of things that I need to check to see if they are in the string, and if so, how many.

推荐答案

您可以使用 map 和 filter 计数具有相同数组值的出现次数:

You can count occurrences with an identical value of an array using map and filter:

let str="I love JavaScript and Node.js ";
let arr=str.replace(/[^a-zA-Z]/g, '').split('');

const mapped = [...new Set(arr)].map(a => `${a} occurs ${arr.filter(a1 => a1 === a).length  } time(s)`);
console.log(mapped);

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