Generate per-minute histogram from timestamps

run.js

const fs = require('fs');

function countTimestamps(timestamps) {
    const ret = new Map();

    timestamps.forEach((timestamp) => {
        ret.set(timestamp, (ret.get(timestamp) || 0) + 1);
    });

    return ret;
}

function getHistogramTSVArray(timestamps) {
    const ret = [];
    const values = [];

    const tsCounts = countTimestamps(timestamps);
    const epochStart = new Date(`${timestamps[0]}Z`).getTime();
    const epochEnd = new Date(`${timestamps[timestamps.length - 1]}Z`).getTime();

    tsCounts.forEach((value, key) => {
        values[(new Date(`${key}Z`).getTime() - epochStart) / 1000 / 60] = value;
    });

    for (let iter = 0; epochStart + iter * 60 * 1000 <= epochEnd; iter += 1) {
        ret.push([new Date(epochStart + iter * 60 * 1000), values[iter] || 0].join('\t'));
    }

    return ret;
}

{
    const src = fs.readFileSync('task-started-timestamps.txt', 'utf-8');
    const timestamps = src.trim().split('\n');

    console.log(getHistogramTSVArray(timestamps).join('\n'));
}