Get a time ago human friendly string from a date (like dates in twitter).

timeago.js

const MINUTE = 60,
  HOUR = MINUTE * 60,
  DAY = HOUR * 24,
  YEAR = DAY * 365;

function getTimeAgo(date) {
  const secondsAgo = Math.round((+new Date() - date) / 1000);

  if (secondsAgo < MINUTE) {
    return secondsAgo + "s";
  } else if (secondsAgo < HOUR) {
    return Math.floor(secondsAgo / MINUTE) + "m";
  } else if (secondsAgo < DAY) {
    return Math.floor(secondsAgo / HOUR) + "h";
  } else if (secondsAgo < YEAR) {
    return date.toLocaleString("default", { day: "numeric", month: "short" });
  } else {
    return date.toLocaleString("default", { year: "numeric", month: "short" });
  }
}

Minor update if you're in need of a slightly more verbose version of this awesome gist that also treats all the time scales equally:

const MINUTE = 60,
  HOUR = MINUTE * 60,
  DAY = HOUR * 24,
  WEEK = DAY * 7,
  MONTH = DAY * 30,
  YEAR = DAY * 365

function getTimeAgo(date) {
  const secondsAgo = Math.round((+new Date() - date) / 1000)
  let divisor = null
  let unit = null

  if (secondsAgo < MINUTE) {
    return secondsAgo + " seconds ago"
  } else if (secondsAgo < HOUR) {
    [divisor, unit] = [MINUTE, 'minute']
  } else if (secondsAgo < DAY) {
    [divisor, unit] = [HOUR, 'hour']
  } else if (secondsAgo < WEEK) {
    [divisor, unit] = [DAY, 'day']
  } else if (secondsAgo < MONTH) {
    [divisor, unit] = [WEEK, 'week']
  } else if (secondsAgo < YEAR) {
    [divisor, unit] = [MONTH, 'month']
  } else if (secondsAgo > YEAR) {
    [divisor, unit] = [YEAR, 'year']
  }

  count = Math.floor(secondsAgo / divisor)
  return  `${count} ${unit}${(count > 1)?'s':''} ago`
}

Edit: Updated to include singular/plural for all time units

Minor update if you're in need of a slightly more verbose version of this awesome gist that also treats all the time scales equally:

const MINUTE = 60,
  HOUR = MINUTE * 60,
  DAY = HOUR * 24,
  WEEK = DAY * 7,
  MONTH = DAY * 30,
  YEAR = DAY * 365

function getTimeAgo(date) {
  const secondsAgo = Math.round((+new Date() - date) / 1000)
  let divisor = null
  let unit = null

  if (secondsAgo < MINUTE) {
    return secondsAgo + " seconds ago"
  } else if (secondsAgo < HOUR) {
    [divisor, unit] = [MINUTE, 'minute']
  } else if (secondsAgo < DAY) {
    [divisor, unit] = [HOUR, 'hour']
  } else if (secondsAgo < WEEK) {
    [divisor, unit] = [DAY, 'day']
  } else if (secondsAgo < MONTH) {
    [divisor, unit] = [WEEK, 'week']
  } else if (secondsAgo < YEAR) {
    [divisor, unit] = [MONTH, 'month']
  } else if (secondsAgo > YEAR) {
    [divisor, unit] = [YEAR, 'year']
  }

  count = Math.floor(secondsAgo / divisor)
  return  `${count} ${unit}${(count > 1)?'s':''} ago`
}

Edit: Updated to include singular/plural for all time units

Just what I needed @rex, thanks! Tiny fix: You are missing const on the count.

Problem is it'll return "1 seconds ago". Here's my modified version:

const MINUTE = 60;
const HOUR = MINUTE * 60;
const DAY = HOUR * 24;
const WEEK = DAY * 7;
const MONTH = DAY * 30;
const YEAR = DAY * 365;

function getTimeAgo(date) {
  const secondsAgo = Math.round((Date.now() - Number(date)) / 1000);

  if (secondsAgo < MINUTE) {
    return secondsAgo + ` second${secondsAgo !== 1 ? "s" : ""} ago`;
  }

  let divisor;
  let unit = "";

  if (secondsAgo < HOUR) {
    [divisor, unit] = [MINUTE, "minute"];
  } else if (secondsAgo < DAY) {
    [divisor, unit] = [HOUR, "hour"];
  } else if (secondsAgo < WEEK) {
    [divisor, unit] = [DAY, "day"];
  } else if (secondsAgo < MONTH) {
    [divisor, unit] = [WEEK, "week"];
  } else if (secondsAgo < YEAR) {
    [divisor, unit] = [MONTH, "month"];
  } else {
    [divisor, unit] = [YEAR, "year"];
  }

  const count = Math.floor(secondsAgo / divisor);
  return `${count} ${unit}${count > 1 ? "s" : ""} ago`;
}