JavaScript

Utils

• Get random item from an array

  arr[Math.floor(Math.random() * arr.length)];

• Capitalize a string

  const capitalize = (string) => string.replace(/^\w/, (c) => c.toUpperCase());
  // or
  // string.charAt(0).toUpperCase() + string.slice(1)

• Format a date string [Intl.DateTimeFormat, toLocaleDateString]

  const formatDate = (dateString) => {
    const options = {
      weekday: 'short',
      year: 'numeric',
      month: 'short',
      day: '2-digit',
      hour: '2-digit',
      minute: '2-digit',
      second: '2-digit',
      hour12: false,
    };
    return new Intl.DateTimeFormat('en', options).format(dateString);
    // or
    // new Date(dateString).toLocaleDateString('en-US', options);
  };
  
  // Usage
  formatDate('1987-07-27T12:34:56'); // Mon, Jul 27, 1987, 12:34:56

• Format a number [Intl.NumberFormat]

  const formatNumber = (number) => {
    const options = {
      notation: 'compact',
      compactDisplay: 'short',
    };
    return new Intl.NumberFormat('en', options).format(number);
  };
  
  // Usage
  formatNumber(123456); // 123K
  formatNumber(456789012); // 457M

• Convert seconds to HH:MM:SS

  const secToHHMMSS = (sec) => {
    let hours = Math.floor(sec / 3600);
    sec %= 3600;
    let minutes = Math.floor(sec / 60);
    let seconds = Math.floor(sec % 60);
  
    hours = hours < 10 ? `0${hours}` : `${hours}`;
    minutes = minutes < 10 ? `0${minutes}` : minutes;
    seconds = seconds < 10 ? `0${seconds}` : seconds;
  
    return `${hours}:${minutes}:${seconds}`;
  };

• Copy text to clipboard

  const copyToClipboard = async (text) => {
    try {
      await navigator.clipboard.writeText(text);
    } catch (error) {
      throw new Error('Cannot copy');
    }
  };

• Padding a string [padStart, padEnd]

  'abc'.padStart(10); // "       abc"
  'abc'.padStart(10, 'foo'); // "foofoofabc"
  'abc'.padStart(6, '123465'); // "123abc"
  'abc'.padStart(8, '0'); // "00000abc"
  
  'abc'.padEnd(10); // "abc       "
  'abc'.padEnd(10, 'foo'); // "abcfoofoof"
  'abc'.padEnd(6, '123456'); // "abc123"
  'abc'.padEnd(1); // "abc"

Node.js/npm

• List all user installed packages

  npm list -g --depth=0

Redirect to another website

[*]

<!-- With HTML `<meta>` tags (not recommended by W3C) -->
<meta http-equiv="refresh" content="0; URL='http://new-website.com'" />

// With JavaScript
window.location = 'http://new-website.com'; // or one of these
window.location.href = 'http://new-website.com';
window.location.assign('http://new-website.com');
window.location.replace('http://new-website.com');