如何定位数组中的对象子集并将属性更改为每个对象的递增数字？

Question

我正在努力对一组对象进行相当复杂的操作。首先这是一个示例数组：[  {id: 11, item: 132, lineNum: 4, linePosition: 5}  {id: 2, item: 124, lineNum: 0, linePosition: 2}  {id: 9, item: 130, lineNum: 0, linePosition: 5}  {id: 12, item: 133, lineNum: 1, linePosition: 3}  {id: 15, item: 136, lineNum: 3, linePosition: 2}  {id: 13, item: 134, lineNum: 0, linePosition: 4}  {id: 10, item: 131, lineNum: 2, linePosition: 1}  {id: 8, item: 129, lineNum: 3, linePosition: 3}  {id: 1, item: 123, lineNum: 0, linePosition: 5}  {id: 3, item: 125, lineNum: 1, linePosition: 7}  {id: 5, item: 127, lineNum: 0, linePosition: 9}  {id: 7, item: 128, lineNum: 1, linePosition: 2}  {id: 4, item: 126, lineNum: 0, linePosition: 4}  {id: 14, item: 135, lineNum: 3, linePosition: 9}]所以我想尽可能高效地按顺序进行以下操作。按 lineNum 对数组进行排序，然后按项目升序排序。然后我想修改每个对象，lineNum === 0使 linePosition 从 0 开始递增。所以第一个匹配对象的 linePosition 为 0，下一个是 1，然后是 2，等等。结果数组如下所示：[  {id: 1, item: 123, lineNum: 0, linePosition: 0}  {id: 2, item: 124, lineNum: 0, linePosition: 1}  {id: 4, item: 126, lineNum: 0, linePosition: 2}  {id: 5, item: 127, lineNum: 0, linePosition: 3}  {id: 9, item: 130, lineNum: 0, linePosition: 4}  {id: 13, item: 134, lineNum: 0, linePosition: 5}  {id: 3, item: 125, lineNum: 1, linePosition: 7}  {id: 7, item: 128, lineNum: 1, linePosition: 2}  {id: 12, item: 133, lineNum: 1, linePosition: 3}  {id: 10, item: 131, lineNum: 2, linePosition: 1}  {id: 8, item: 129, lineNum: 3, linePosition: 3}  {id: 14, item: 135, lineNum: 3, linePosition: 9}  {id: 15, item: 136, lineNum: 3, linePosition: 2}  {id: 11, item: 132, lineNum: 4, linePosition: 5}]

Answer 1

Array.prototype.sort()

let arr = getData();

arr.sort(function(a, b) {

  if( a.lineNum === b.lineNum ) {

    return a.item - b.item;

  } else {

    return a.lineNum - b.lineNum;

  }

});

// return a.lineNum === b.lineNum ? a.item - b.item : a.lineNum - b.lineNum;

for( let i = 0; i < arr.length; i++ ) {

  if( arr[i].lineNum > 0 ) break;

  arr[i].linePosition = i;

}

// Used classic loop, to break it and avoid unnecessary iterations.

console.log( JSON.stringify(arr).replace(/\},/g, "},\n") );

/***/

function getData() {

  return [

    {id: 11, item: 132, lineNum: 4, linePosition: 5},

    {id: 2, item: 124, lineNum: 0, linePosition: 2},

    {id: 9, item: 130, lineNum: 0, linePosition: 5},

    {id: 12, item: 133, lineNum: 1, linePosition: 3},

    {id: 15, item: 136, lineNum: 3, linePosition: 2},

    {id: 13, item: 134, lineNum: 0, linePosition: 4},

    {id: 10, item: 131, lineNum: 2, linePosition: 1},

    {id: 8, item: 129, lineNum: 3, linePosition: 3},

    {id: 1, item: 123, lineNum: 0, linePosition: 5},

    {id: 3, item: 125, lineNum: 1, linePosition: 7},

    {id: 5, item: 127, lineNum: 0, linePosition: 9},

    {id: 7, item: 128, lineNum: 1, linePosition: 2},

    {id: 4, item: 126, lineNum: 0, linePosition: 4},

    {id: 14, item: 135, lineNum: 3, linePosition: 9},

  ];

}

.as-console-wrapper { max-height: 100vh !important; }

Answer 2

您可以使用 Javascript.sort()函数完成上述任务。它可以采用可选的比较函数参数，该参数指定定义排序顺序的函数。

let arr = [

  {id: 11, item: 132, lineNum: 4, linePosition: 5},

  {id: 2, item: 124, lineNum: 0, linePosition: 2},

  {id: 9, item: 130, lineNum: 0, linePosition: 5},

  {id: 12, item: 133, lineNum: 1, linePosition: 3},

  {id: 15, item: 136, lineNum: 3, linePosition: 2},

  {id: 13, item: 134, lineNum: 0, linePosition: 4},

  {id: 10, item: 131, lineNum: 2, linePosition: 1},

  {id: 8, item: 129, lineNum: 3, linePosition: 3},

  {id: 1, item: 123, lineNum: 0, linePosition: 5},

  {id: 3, item: 125, lineNum: 1, linePosition: 7},

  {id: 5, item: 127, lineNum: 0, linePosition: 9},

  {id: 7, item: 128, lineNum: 1, linePosition: 2},

  {id: 4, item: 126, lineNum: 0, linePosition: 4},

  {id: 14, item: 135, lineNum: 3, linePosition: 9}

];

//sorting the given array, first based on lineNum, then by item

arr.sort(function(a,b){

  if(a.lineNum !== b.lineNum)

    return a.lineNum - b.lineNum;

  return a.item - b.item;

});

// modify each object where lineNum===0, linePosition starting from 0

// since we have sorted, break when first lineNum > 0

let linePos = 0;

for( let i = 0; i < arr.length; i++ ) {

  if( arr[i].lineNum > 0 ) 

    break;

  if(arr[i].lineNum === 0)

    arr[i].linePosition = linePos++;

}

//   console.log(arr); //<-- This prints as array

console.log( JSON.stringify(arr).replace(/\},/g, "},\n") ); // <-- This prints your mentioned format