漢数字を整数に

kanToNum.js

// 漢字で表した整数を整数の数値として返す

const kanToNum = (knum="三百二十一")=>{
  const or=(a,b)=>a==null ? b : a;
  const numb = new Map()
    .set("零",0).set("一",1).set("二",2).set("三",3).set("四",4)
    .set("五",5).set("六",6).set("七",7).set("八",8).set("九",9);
  const places = new Map()
    .set("十",10).set("百",100).set("千",1000).set("万",10000)
    .set("億",10**8).set("兆",10**12).set("京",10**16).set("垓",10**20);
  const stack = [];
  for (let i=0;i<knum.length;i++){
    if (numb.has(knum[i])){
      stack.push(numb.get(knum[i]))
    }if (places.get(knum[i]) > or(numb.get(knum[i-1]), places.get(knum[i-1]))){
      stack.push(stack.pop() * places.get(knum[i]))
    }else if (places.has(knum[i])){
      stack.push(places.get(knum[i]))
    }
  }
  for (let i=0;i<knum.length;i++){
    stack.push(stack.pop()+(stack.pop()||0))
  }
  return stack.pop()
}