如何在 JavaScript 中计算字符串中特定字符串的出现次数

javascriptweb developmentfront end technologyobject oriented programming

我们需要编写一个 JavaScript 函数，该函数接受两个字符串，例如 str1 和 str2。然后该函数应计算并返回 str2 在 str1 中出现的次数'

例如 −

count('this is a string', 'is') should return 2;

示例

其代码为 −

const str1 = 'this is a string';
const str2 = 'is';
const countOccurrences = (str1, str2, allowOverlapping = true) => {
   str1 += "";
   str2 += "";
   if (str2.length <= 0) return (str1.length + 1);
   var n = 0,
   pos = 0,
   step = allowOverlapping ? 1 : str2.length;
   while (true) {
      pos = str1.indexOf(str2, pos);
      if (pos >= 0) {
         ++n;
         pos += step;
      } else break;
   }
   return n;
};
console.log(countOccurrences(str1, str2));