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How to group files in array of objects deponds on the number of pages of each one

August 10, 2022

I’ve got an array of objects:
Input

[
  { file: '1.pdf', text: 'Page: 1 / 2' },
  { file: '2.pdf', text: 'Page: 2 / 2' },
    // -- '1.pdf':['1.pdf','2.pdf']
  { file: '3.pdf', text: 'Page: 1 / 3' },
  { file: '4.pdf', text: 'Page: 2 / 3' },
  { file: '5.pdf', text: 'Page: 3 / 3' },
    // -- '2.pdf':['3.pdf','4.pdf', '5.pdf']
  { file: '6.pdf', text: 'Page: 1 / 4' },
  { file: '7.pdf', text: 'Page: 2 / 4' },
  { file: '8.pdf', text: 'Page: 3 / 4' },
  { file: '9.pdf', text: 'Page: 4 / 4' }
    // -- '3.pdf':['6.pdf','7.pdf', '8.pdf', '9.pdf']
]

And I wanna group them deponds on the number of pages of each one like this Output:

{
  "1.pdf": ["1.pdf", "2.pdf"],
  "2.pdf": ["3.pdf", "4.pdf", "5.pdf"],
  "3.pdf": ["6.pdf", "7.pdf", "8.pdf", "9.pdf"],
};

My Attempt:

let arr = [
  { file: "1.pdf", text: "Page: 1 / 2" },
  { file: "2.pdf", text: "Page: 2 / 2" },
  { file: "3.pdf", text: "Page: 1 / 3" },
  { file: "4.pdf", text: "Page: 2 / 3" },
  { file: "5.pdf", text: "Page: 3 / 3" },
  { file: "6.pdf", text: "Page: 1 / 4" },
  { file: "7.pdf", text: "Page: 2 / 4" },
  { file: "8.pdf", text: "Page: 3 / 4" },
  { file: "9.pdf", text: "Page: 4 / 4" },
];
let result = {};
let i = 0;
let x = null;
let visited = [];
for (const { file, text } of arr) {
  let val = text.split("/").at(-1).trim();
  let key = null;
  if (!visited.includes(val)) {
    key = ++i + ".pdf";
    x = key;
    visited.push(val);
  } else {
    key = x;
  }
  result[key] ??= [];
  result[key].push(file);
}

console.log(result);

This works well in case where there’s unique number of pages, BUT When there’s the same number of pages on other it fails and combines them all to one instead of create new one:

[
  { file: '1.pdf', text: 'Page: 1 / 2' },
  { file: '2.pdf', text: 'Page: 2 / 2' },
  { file: '3.pdf', text: 'Page: 1 / 3' },
  { file: '4.pdf', text: 'Page: 2 / 3' },
  { file: '5.pdf', text: 'Page: 3 / 3' },
  { file: '6.pdf', text: 'Page: 1 / 4' },
  { file: '7.pdf', text: 'Page: 2 / 4' },
  { file: '8.pdf', text: 'Page: 3 / 4' },
  { file: '9.pdf', text: 'Page: 4 / 4' },
  { file: '10.pdf', text: 'Page: 1 / 2' },
  { file: '11.pdf', text: 'Page: 2 / 2' },
]

Output:

{
  "1.pdf": ["1.pdf", "2.pdf"],
  "2.pdf": ["3.pdf", "4.pdf", "5.pdf"], //      vvvvvvvvvvvvvvvvvv
  "3.pdf": ["6.pdf", "7.pdf", "8.pdf", "9.pdf", "10.pdf", "11.pdf"],
};

Expected Output:

{
  "1.pdf": ["1.pdf", "2.pdf"],
  "2.pdf": ["3.pdf", "4.pdf", "5.pdf"],
  "3.pdf": ["6.pdf", "7.pdf", "8.pdf", "9.pdf"],
  "4.pdf": ["10.pdf", "11.pdf"],
};

>Solution :

CODE

var array = [
  { file: '1.pdf', text: 'Page: 1 / 2' },
  { file: '2.pdf', text: 'Page: 2 / 2' },
  { file: '3.pdf', text: 'Page: 1 / 3' },
  { file: '4.pdf', text: 'Page: 2 / 3' },
  { file: '5.pdf', text: 'Page: 3 / 3' },
  { file: '6.pdf', text: 'Page: 1 / 4' },
  { file: '7.pdf', text: 'Page: 2 / 4' },
  { file: '8.pdf', text: 'Page: 3 / 4' },
  { file: '9.pdf', text: 'Page: 4 / 4' },
  { file: '10.pdf', text: 'Page: 1 / 2' },
  { file: '11.pdf', text: 'Page: 2 / 2' },
];

var ret = {};
var lastGroup = 0;

array.forEach(function (value, i) {
    if(value.text.includes("Page: 1 /")){
        lastGroup++;
        ret[lastGroup + ".pdf"]=[];
    }
    ret[lastGroup + ".pdf"].push(value.file);
});

console.log(ret);

OUTPUT

{
  "1.pdf": [
    "1.pdf",
    "2.pdf"
  ],
  "2.pdf": [
    "3.pdf",
    "4.pdf",
    "5.pdf"
  ],
  "3.pdf": [
    "6.pdf",
    "7.pdf",
    "8.pdf",
    "9.pdf"
  ],
  "4.pdf": [
    "10.pdf",
    "11.pdf"
  ]
}