如何在 JavaScript 中分离每个 JSON 对象并将它们分组到一个数组中？

Question

来自 multer.js 的 req.files 示例[    {        fieldname: files0,        originalname: 'Screenshot from 2020-05-23 01-52-30.png',        encoding: '7bit',        mimetype: 'image/png',        destination: 'public/uploads/projects/0a480789-eb14-4fe4-bb89-44aa741efe33/proposals/chma00000133',        filename: '1606822252923_Screenshot from 2020-05-23 01-52-30.png',        path: 'public/uploads/projects/0a480789-eb14-4fe4-bb89-44aa741efe33/proposals/chma00000133/1606822252923_Screenshot from 2020-05-23 01-52-30.png',        size: 172092      },      {        fieldname: files0,        originalname: 'Screenshot from 2020-05-22 08-44-05.png',        encoding: '7bit',        mimetype: 'image/png',        destination: 'public/uploads/projects/0a480789-eb14-4fe4-bb89-44aa741efe33/proposals/chma00000133',        filename: '1606822252925_Screenshot from 2020-05-22 08-44-05.png',        path: 'public/uploads/projects/0a480789-eb14-4fe4-bb89-44aa741efe33/proposals/chma00000133/1606822252925_Screenshot from 2020-05-22 08-44-05.png',        size: 440592      },      {        fieldname: files1,        originalname: 'Screenshot from 2020-05-30 11-36-42.png',        encoding: '7bit',        mimetype: 'image/png',        destination: 'public/uploads/projects/0a480789-eb14-4fe4-bb89-44aa741efe33/proposals/chma00000133',        filename: '1606822252930_Screenshot from 2020-05-30 11-36-42.png',        path: 'public/uploads/projects/0a480789-eb14-4fe4-bb89-44aa741efe33/proposals/chma00000133/1606822252930_Screenshot from 2020-05-30 11-36-42.png',        size: 477511      },我想动态地将每个 JSON 对象与其字段名分组，并将它们存储在对象数组中，同时使用它们的字段名编号作为数组索引。组可以在 0 到 9 之间，具体取决于用户输入。

Answer 1

我会使用减少

const data = [ 

{ fieldname: 'files0', originalname: 'Screenshot from 2020-05-23 01-52-30.png', },

{ fieldname: 'files0', originalname: 'Screenshot from 2020-05-22 08-44-05.png', },

{ fieldname: 'files1', originalname: 'Screenshot from 2020-05-30 11-36-42.png', },

{ fieldname: 'files1', originalname: 'Screenshot from 2020-05-30 11-36-36.png', },

{ fieldname: 'files1', originalname: 'Screenshot from 2020-05-30 11-36-31.png', }],

arr = data.reduce((acc, cur) => {

  const idx = cur.fieldname.replace("files",""); // get 0, 1

  if (acc[idx]) acc[idx].push(cur); // if already there, just push

  else acc[idx] = [cur];            // otherwise initialise

  return acc;

},[]) 

console.log(arr)

注意：组可以在 0 到 9 之间，具体取决于用户输入。

我假设没有漏洞，因为这可能会导致稀疏数组，所以

data = [ 

     { fieldname : 'files0' },

     { fieldname : 'files0' },

     { fieldname : 'files3' },

     { fieldname : 'files3' },

 }

会创建一个数组

[

  [ { fieldname : 'files0' }, { fieldname : 'files0' } ],

  null,

  null,

  [ { fieldname : 'files3' }, { fieldname : 'files3' } ],

]

Answer 2

我尽量不修改你的逻辑来做到这一点。

如果没有files2，filesArray[2] 将为undefined。

// Omit other fields

const req = {

    files: [

        { fieldname: "files0", originalname: 'Screenshot from 2020-05-23 01-52-30.png'},

        { fieldname: "files0", originalname: 'Screenshot from 2020-05-22 08-44-05.png'},

        { fieldname: "files1", originalname: 'Screenshot from 2020-05-30 11-36-42.png'},

        { fieldname: "files1", originalname: 'Screenshot from 2020-05-30 11-36-36.png'},

        { fieldname: "files1", originalname: 'Screenshot from 2020-05-30 11-36-31.png'},

        { fieldname: "files3", originalname: 'Screenshot from 2020-05-30 11-36-42.png'},

        { fieldname: "files3", originalname: 'Screenshot from 2020-05-30 11-36-36.png'},

        { fieldname: "files3", originalname: 'Screenshot from 2020-05-30 11-36-31.png'}

    ]

}

let filesArray = []

for (let file of req.files) {

    const thisFileGroup = parseInt(file.fieldname.match(/\d/g).join(''), 10);

    if (!filesArray[thisFileGroup]) {

        filesArray[thisFileGroup] = []

    }

    filesArray[thisFileGroup].push(file)

}

console.log(filesArray[2]) // will be undefined

console.log(filesArray[1]) // will be files1 array

console.log(filesArray)

Answer 3

如果您不一定需要按索引排序files[index]

在这种情况下，你可以将Array.prototype.reduce()转换为Object。
您的对象将按属性（但不是按字母顺序）分组，其中包含一个数组，其中的项目具有相同的属性键。使用Object.values() （如果需要，还可以使用Array.prototype.forEach()） 迭代您的对象。fieldname

const data = [

  { fieldname: "files0", originalname: '0-a'},

  { fieldname: "files0", originalname: '0-b'},

  { fieldname: "files1", originalname: '1-a'},

  { fieldname: "files1", originalname: '1-b'},

  { fieldname: "files1", originalname: '1-c'},

];

const byFieldName = data.reduce((ob, d) => {

  if (!ob.hasOwnProperty(d.fieldname)) ob[d.fieldname] = [];

  ob[d.fieldname].push(d);

  return ob;

}, {});

// console.log(byFieldName); // Uncomment to see how it looks like

console.log( Object.values(byFieldName) );