Question

在打字稿中：

我有一个一维对象数组：my1dArray。

我将my1dArray的每行5倍复制到2D数组my2dArray中（所以我最终得到了my2dArray[3][5]）。

然后我重置my2dArray每行的id元素。

对于my2dArray[0]，我最终得到了这个（id = 4）：

{id: 4, surname: "Smith", givenNames: "Linda"}
{id: 4, surname: "Smith", givenNames: "Linda"}
{id: 4, surname: "Smith", givenNames: "Linda"}
{id: 4, surname: "Smith", givenNames: "Linda"}
{id: 4, surname: "Smith", givenNames: "Linda"}

我以为我会得到的是

{id: 0, surname: "Smith", givenNames: "Linda"}
{id: 1, surname: "Smith", givenNames: "Linda"}
{id: 2, surname: "Smith", givenNames: "Linda"}
{id: 3, surname: "Smith", givenNames: "Linda"}
{id: 4, surname: "Smith", givenNames: "Linda"}

my2dArray[4][5]数组的其余部分也有相同的问题。

我在做什么错了？

//Create 1d Array
let my1dArray: any[];
my1dArray = [

      { id: 0, surname: 'Smith', givenNames: 'Linda'},
      { id: 0, surname: 'Bloggs', givenNames: 'Bill'},
      { id: 0, surname: 'Jones', givenNames: 'Jim'},

];


//Initalise 2d Array
let my2dArray = init2DArray(3, 5, function () {

      return 0

});


let j = 0;
let k = 0;
for (let i = 0; i < my1dArray.length; i++) {

      for (let count = 0; count < 5; count++) {

          my2dArray[j][count] = my1dArray[i];
          //reset the id
          my2dArray[j][count].id = k;
          k++;
      }



    j++;

}

console.log('myNewData', my2dArray[0]);




/////Intialisation function///////////////

function init2DArray(xlen, ylen, factoryFn) {

      let ret = [];

      for (let x = 0; x < xlen; x++) {
          ret[x] = [];
          for (let y = 0; y < ylen; y++) {
              ret[x][y] = factoryFn(x, y)
          }
      }

  return ret
}

Answer 1

实际上，您并不复制my1dArray的每一行。此作业：

my2dArray[j][count] = my1dArray[i];

仅使用对my2dArray中相同对象的引用来填充my1dArray。因此，当您更改id时，每次在您的内部循环中都对同一个对象执行此操作。

要在JS中正确复制对象，您可能需要阅读this。对于浅表副本（足够用于示例代码），可以使用Object.assign()。

下面的工作代码段：

//Create 1d Array
let my1dArray: any[];
my1dArray = [{
    id: 0,
    surname: 'Smith',
    givenNames: 'Linda'
  },
  {
    id: 0,
    surname: 'Bloggs',
    givenNames: 'Bill'
  },
  {
    id: 0,
    surname: 'Jones',
    givenNames: 'Jim'
  },
];


//Initalise 2d Array
let my2dArray = init2DArray(3, 5, function() {
  return 0
});

let j = 0;
let k = 0;
for (let i = 0; i < my1dArray.length; i++) {
  for (let count = 0; count < 5; count++) {
    my2dArray[j][count] = Object.assign({}, my1dArray[i]);
    //reset the id
    my2dArray[j][count].id = k;
    k++;
  }
  j++;
}


function init2DArray(xlen, ylen, factoryFn) {
  let ret = [];
  for (let x = 0; x < xlen; x++) {
    ret[x] = [];
    for (let y = 0; y < ylen; y++) {
      ret[x][y] = factoryFn(x, y)
    }
  }
  return ret
}

console.log(my2dArray)

如何将数据从一维数组转换为对象的二维数组并更改某些元素？

1 个答案: