Simple Vue.js filters that I usually need

gistfile1.js

/**
 * Changes value to past tense.
 * Simple filter does not support irregular verbs such as eat-ate, fly-flew, etc.
 * http://jsfiddle.net/bryan_k/0xczme2r/
 *
 * @param {String} value The value string.
 */
Vue.filter('past-tense', function(value) {
  // Slightly follows http://www.oxforddictionaries.com/us/words/verb-tenses-adding-ed-and-ing
  var vowels = ['a', 'e', 'i', 'o', 'u'];
  if(!value) {
    return;
  }

  var last = value.toLowerCase().substr(value.length - 1),
    secondLast = value.toLowerCase().substr(value.length - 2, 1),
    thirdLast = value.toLowerCase().substr(value.length - 3, 1),
    lastTwo = value.toLowerCase().substr(value.length - 2),
    lastThree = value.toLowerCase().substr(value.length - 3),
    inArray = function(ar, value) {
        return ar.indexOf(value) != -1
    };

  // participle or already past tense, don't want
  if(lastThree === 'ing' || lastTwo === 'ed') {
    return value;
  }

  // Ends in 'e', simply add the 'd'
  if(last === 'e') {
    return value + 'd';
  }
  
  // Ends in 'c', add the 'ked'
  if(last === 'c') {
    return value + 'ked';
  }
  
  // Ends with consonant, vowel, consonant. I'm simple, double consonant and add 'ed'
  if(!inArray(vowels, thirdLast) && inArray(vowels, secondLast) && !inArray(vowels, last)) {
      return value + last + 'ed';
  }

  return value + 'ed';
});

/**
 * Vue filter to convert a slug to a more human friendly form.
 *
 * @param {String} value The value string.
 */
Vue.filter('humanable', function(value) {
  var words = value.split(/[-_]+/g);
  var results = [];
  for(var i=0; i < words.length; i++) {
    var letter = words[i].charAt(0).toUpperCase();
    results.push(letter + words[i].slice(1));
  }
  return results.join(' ');
});

/**
 * Vue filter to convert the given value to percent.
 * http://jsfiddle.net/bryan_k/qauf3qyh/
 *
 * @param {String} value    The value string.
 * @param {Number} decimals The number of decimal places.
 */
Vue.filter('percentage', function(value, decimals) {
  if(!value) {
    value = 0;
  }

  if(!decimals) {
    decimals = 0;
  }

  value = value * 100;
  value = Math.round(value * Math.pow(10, decimals)) / Math.pow(10, decimals);
  value = value + '%';
  return value;
});


/**
 * Vue filter to round the decimal to the given place.
 * http://jsfiddle.net/bryan_k/3ova17y9/
 *
 * @param {String} value    The value string.
 * @param {Number} decimals The number of decimal places.
 */
Vue.filter('round', function(value, decimals) {
  if(!value) {
    value = 0;
  }

  if(!decimals) {
    decimals = 0;
  }

  value = Math.round(value * Math.pow(10, decimals)) / Math.pow(10, decimals);
  return value;
});


/**
 * Vue filter to convert the given value to whole dollars, no change.
 * http://jsfiddle.net/bryan_k/2t6bqqfc/
 *
 * @param {String} value The value string.
 */
Vue.filter('no-change', function(value, symbol) {
  if(!value) {
    value = 0;
  }
  
  if(!symbol) {
      symbol = '$';
  }
  
  value = value.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',').split('.')[0];
  return symbol + value;
});

/**
 * Vue filter to make a simple timestamp for an ISO date.
 * http://jsfiddle.net/bryan_k/44kqtpeg/
 *
 * @param {String} value The value string.
 */
Vue.filter('timestamp', function(value) {
  var parts = value.split(' ');
  var date = parts[0];
  var time = parts[1];
  
  date = date.split('-');
  time = time.split(':');
    
  if(parseInt(time[0], 10) > 12) {
    var hour = parseInt(time[0], 10) % 12;
  }
  else {
   var hour = parseInt(time[0], 10);
  }
    
  hour = hour < 10 ? '0' + hour : hour;
    
  return '[' + date[1] + '/' + date[2] + ' ' + hour + ':' + time[1] + ']';
});

/**
 * Vue filter to truncate a string to the specified length.
 * @param {String} value The value string.
 */
Vue.filter('truncate', function(value, length) {
  if(value.length < length) {
    return value;
  }

  length = length - 3;

  return value.substring(0, length) + '...';
});