日期解析及日期格式化示例

[taoeer]

const formatingTokens = /YYYY|YY|MM?|DD?/g;

const expressions = {
  YYYY: {
    reg: /\d{4}/,
    parse(input) {
      this.year = +input;
    },
  },
  YY: {
    reg: /\d{2}/,
    parse(input) {
      this.year = +input + 2000;
    },
  },
  MM: {
    reg: /\d{2}/,
    parse(input) {
      this.month = +input - 1;
    },
  },
  M: {
    reg: /\d/,
    parse(input) {
      this.month = +input - 1;
    },
  },
  DD: {
    reg: /\d{2}/,
    parse(input) {
      this.date = +input;
    },
  },
};

Date.prototype.format = function(fmt) { 
    var o = { 
       "M+" : this.getMonth()+1,                 //月份 
       "d+" : this.getDate(),                    //日 
       "h+" : this.getHours(),                   //小时 
       "m+" : this.getMinutes(),                 //分 
       "s+" : this.getSeconds(),                 //秒 
       "q+" : Math.floor((this.getMonth()+3)/3), //季度 
       "S"  : this.getMilliseconds()             //毫秒 
   }; 
   if(/(y+)/.test(fmt)) {
           fmt=fmt.replace(RegExp.$1, (this.getFullYear()+"").substr(4 - RegExp.$1.length)); 
   }
    for(var k in o) {
       if(new RegExp("("+ k +")").test(fmt)){
            fmt = fmt.replace(RegExp.$1, (RegExp.$1.length==1) ? (o[k]) : (("00"+ o[k]).substr((""+ o[k]).length)));
        }
    }
   return fmt; 
} 

function parse(input, format) {
  const date = {};
  const tokens = format.matchAll(formatingTokens);
  for (const token of tokens) {
    const str = input.substr(token.index, token[0].length);
    expressions[token[0]].parse.call(date, str);
  }
  console.log(date.year, date.month, date.date);
  return new Date(date.year, date.month, date.date, 0, 0, 0);
}

console.log(parse("05-20-2022", "MM-DD-YYYY").toLocaleString());
console.log(parse("05-20-2022", "MM-DD-YYYY").format("yyyy-MM-dd"));