题解 | #计算某字符出现次数#filter

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

void async function () {
    let line = (await readline()).toUpperCase().split("");
    let c = (await readline()).toUpperCase();
    console.log(line.filter(item=>item==c).length||0)
}()