数组合并成一个前,一个后的样子?

        let a = [
          ["1995-09-01"],
          ["1998-09-01"],
          ["2001-09-01"],
          ["2003-08-01"],
          ["2004-01-01"],
          ["2008-07-01"],
          ["2009-03-01"],
          ["2010-07-01"],
          ["2014-07-01"],
          ["2015-01-01"],
          ["2021-10-27"]
        ]
        let b = [
          ["1998-07-31"],
          ["2001-07-31"],
          ["2003-07-31"],
          ["2008-06-30"],
          ["2007-01-01"],
          ["2009-02-28"],
          ["2010-06-30"],
          ["2014-06-30"],
          ["2021-10-27"],
          ["2020-01-01"],
          ["2021-10-27"]
        ]

怎么合并成这种一前一后的样子:

   let a = [
      ["1995-09-01"],
      ["1998-09-01"],
      ["2001-09-01"],
      ["2003-08-01"],
      ["2004-01-01"],
      ["2008-07-01"],
      ["2009-03-01"],
      ["2010-07-01"],
      ["2014-07-01"],
      ["2015-01-01"],
      ["2021-10-27"],
    ];
    let b = [
      ["1998-07-31"],
      ["2001-07-31"],
      ["2003-07-31"],
      ["2008-06-30"],
      ["2007-01-01"],
      ["2009-02-28"],
      ["2010-06-30"],
      ["2014-06-30"],
      ["2021-10-27"],
      ["2020-01-01"],
      ["2021-10-27"],
    ];
    a.forEach((item,index) => {
      console.log([...item, ...b[index]]);
    })

没理解什么叫一前一后

for( let i = 0;i<a.length;i++){
a[i].push(b[i][0]);
}
(具体i长度自己定)

蠢办法
var c = []; for(var i = 0; i < a.length; i++) c = c.concat([a[i]], [b[i]]);

有用望采纳

  const c = a.map((cur, index) => {
    return [...cur, ...b[index]];
  })

  console.log(c)