Question 177328 in Javascript Question posted in
A very good W3school tutorial can be found here.

Can Javascript merge data based on a key?

I have this data:

[
  {
    "key": 111,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ]
  },
  {
    "key": 222,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ]
  },
  {
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 111
    }
  },
  {
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 222
    }
  }
]

Now I need to merge the data based on the key. For suppose if the objects contain the key"111" all the related info should be displayed as one obj

Example output:

[
  {
    "key": 111,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ],
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 111
    }
  },
  {
    "key": 222,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ],
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 222
    }
  }
]

UPDATE:
Based on Hao Wu answer I get the following output

[
  {
    "key": 111,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ]
  },
  {
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 222
    }
  }
]

Entire Code:

const fs = require("fs");
var util = require('util');
const path = require("path");
const { ObjectFlags } = require('typescript');
const { join } = require('path');
const { stringify } = require('querystring');
const _ = require('lodash');

let rawdata = fs.readFileSync('./sample_data.json');
let jsondata = JSON.parse(rawdata);

let stud_records=[];
for (let i = 0; i < jsondata.records.length; i++) {
    let obj = jsondata.records[i];
    let key = obj.id;
    let studentInfo = jsondata.records[i].data;
    let data = {
      studentInfo: [studentInfo],
      key: key
    };
    stud_records.push(data);
  }

  let conf_records=[];
  for (let i = 0; i < Object.values(jsondata.conf_data).length; i++) {
    let obj = Object.values(jsondata.conf_data)[i];
    let key = Object.values(jsondata.conf_data)[i].id;
    let position = i+1;
    let confidential = Object.values(jsondata.conf_data)[i];
    let data = {
      confidential: {
        data:confidential,
        key:key,
        position: position
      },
    };
    conf_records.push(data);
  }

let joined_data= stud_records.concat(conf_records)

const merged = Object.values(joined_data.reduce((acc, cur) => {
  const key = cur.confidential?.key ?? cur.key;
  if (key)
    acc[key] = { ...acc[key], ...cur };
  return acc;
}, {}));

var log_file = fs.createWriteStream(__dirname + '/output.json', {flags : 'w'});
var log_stdout = process.stdout;

console.log = function(d) { //
  log_file.write(util.format(d) + 'n');
  log_stdout.write(util.format(d) + 'n');
};

console.log(JSON.stringify(merged, null, 2))
Tags:

2

Answers


  1. 0

    Based on your structure, this code can do the job:

    const t = [
  {
    key: 111,
    studentInfo: [
      {
        details: {
          calculated_fields: null,
          status: false,
        },
      },
    ],
  },
  {
    key: 222,
    studentInfo: [
      {
        details: {
          calculated_fields: null,
          status: false,
        },
      },
    ],
  },
  {
    confidential: {
      data: {
        access_control: {
          private_data: null,
          users: [],
        },
      },
      key: 111,
    },
  },
  {
    confidential: {
      data: {
        access_control: {
          private_data: null,
          users: [],
        },
      },
      key: 222,
    },
  },
];

const res = [];

t.reduce((output, currentObj) => {
  currentObj.key
    ? output.push(currentObj)
    : Object.assign(
        output.find((o) => o.key === currentObj.confidential.key),
        currentObj
      );
  return output;
}, res);

console.log(res);
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  2. 0

    Here’s a solution using Array.prototype.reduce:

    const data = [
  {
    "key": 111,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ]
  },
  {
    "key": 222,
    "studentInfo": [
      {
        "details": {
          "calculated_fields": null,
          "status": false
        }
      }
    ]
  },
  {
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 111
    }
  },
  {
    "confidential": {
      "data": {
        "access_control": {
          "private_data": null,
          "users": []
        }
      },
      "key": 222
    }
  }
];

const merged = Object.values(data.reduce((acc, cur) => {
  const key = cur.confidential?.key ?? cur.key;
  if (key)
    acc[key] = { ...acc[key], ...cur };
  return acc;
}, {}));

console.log(merged);
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