完成将 toChineseNum， 可以将数字转换成中文大写的表示，处理到万级别，例如 toChineseNum(12345)，返回 一万二千三百四十五

const toChineseNum = (num) => {
			  const unit = ['', '十', '百', '千']
			  const counts = ['零', '一', '二', '三', '四', '五', '六', '七', '八', '九']

			  const pre = Math.floor(num / 10000)
			  const next = num % 10000

			  let getfour = (mynum, flag = false) => {
			        if(!mynum){return ''}
			  	let i = 0, str = ''

			  	while(flag ? i < 4 : mynum > 0 ) {
			  		count = mynum % 10
			  		mynum = Math.floor(mynum / 10)
			  		str = (count ? counts[count] + unit[i] : str[0] == '零' ? '' : str.length && i ? '零' : '') + str
			  		i++
			  	}
			  	return str
			  }

			  return pre ? getfour(pre) + '万' + getfour(next, true) : getfour(num)
			}
    		console.log(toChineseNum(59900670))