Object specific merge

merge.js

const util = require("util");
const { performance } = require("perf_hooks");

// Input data is like this
const exampleInput = [
  { 9668: { "Fa0/11": { in_traffic: "1000" } } },
  { 9668: { "Fa0/11": { out_traffic: "900" } } },
  { 9628: { "Fa0/16": { in_traffic: "800" } } },
];

// Wanted output:
const output = {
  9668: { 'Fa0/11': { in_traffic: '1000', out_traffic: '900' } },
  9628: { 'Fa0/16': { in_traffic: '800' } },
};

const merge = (data) => {
  //generates hashmap
  let hm = {};
  for (let i = 0; i < data.length; i++) {
    let keyAtIndex = Object.keys(data[i])[0]; //We only need the first and only key
    hm[keyAtIndex]
      ? (hm[keyAtIndex] = [...hm[keyAtIndex], i])
      : (hm[keyAtIndex] = [i]);
  }

  //start merging
  let merged = [];
  for (let k in hm) {
    let arr = hm[k];
    let obj = {};
    arr.forEach((e) => {
      //deep merge
      let deepKey = Object.keys(data[e][k])[0];
      obj = { ...obj, [deepKey]: { ...obj[deepKey], ...data[e][k][deepKey] } };
    });
    merged.push({ [k]: obj });
  }
  return merged;
};

const createBenchmarkData = (n) => {
  let data = [];
  for (let i = 1; i < n; i++) {
    let sameItems = Math.floor(Math.random() * Math.floor(4)) + 1;
    for (let j = 1; j <= sameItems; j++) {
      data.push({
        [i]: {
          [`Fa0${i}`]: {
            [j % 2 === 0 ? "in_traffic" : "out_traffic"]: i * 1000,
          },
        },
      });
    }
  }
  return data;
};

let data = createBenchmarkData(110000);
let pre = performance.now();
let d = merge(data);
let after = performance.now();
console.log("Length of data pre-merge: ", data.length);
console.log("Length of data post-merge: ", d.length);
console.log(`Merging with n = ${data.length} took ${after - pre} ms`);