题解 | 计算某字符出现次数

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    //定义变量
        let count = 0
        let str = await readline();  // 读取第一行字符串
        let c  =  await readline(); //读取第二次输入的特定字符
        //判断特定的字符是数字还是英文字母
        if(/[a-zA-Z]/.test(c)){
            let lowc = c.toLowerCase() //小写
            let  upc = c.toUpperCase() //大写
           //遍历去对比每个字符 
           for(let char of  str){
               if(char===lowc || char===upc){
                  count++;
               }
           }

        }else if(/[0-9]/.test(c) ){
           for(let char of  str){
               if(char=== c){
                  count++;
               }
           } 

        }
        console.log(count)
}()