bootstrap-maxlength.js

(function ($) {
  'use strict';
  /**
   * We need an event when the elements are destroyed
   * because if an input is removed, we have to remove the
   * maxlength object associated (if any).
   * From:
   * http://stackoverflow.com/questions/2200494/jquery-trigger-event-when-an-element-is-removed-from-the-dom
   */
  if (!$.event.special.destroyed) {
    $.event.special.destroyed = {
      remove: function (o) {
        if (o.handler) {
          o.handler();
        }
      }
    };
  }


  $.fn.extend({
    maxlength: function (options, callback) {
      var documentBody = $('body'),
        defaults = {
          showOnReady: false, // true to always show when indicator is ready
          alwaysShow: false, // if true the indicator it's always shown.
          threshold: 10, // Represents how many chars left are needed to show up the counter
          warningClass: 'label label-success',
          limitReachedClass: 'label label-important label-danger',
          separator: ' / ',
          preText: '',
          postText: '',
          showMaxLength: true,
          placement: 'bottom',
          message: null, // an alternative way to provide the message text
          showCharsTyped: true, // show the number of characters typed and not the number of characters remaining
          validate: false, // if the browser doesn't support the maxlength attribute, attempt to type more than
          // the indicated chars, will be prevented.
          utf8: false, // counts using bytesize rather than length. eg: '£' is counted as 2 characters.
          appendToParent: false, // append the indicator to the input field's parent instead of body
          twoCharLinebreak: true,  // count linebreak as 2 characters to match IE/Chrome textarea validation. As well as DB storage.
          customMaxAttribute: null,  // null = use maxlength attribute and browser functionality, string = use specified attribute instead.
          allowOverMax: false
          // Form submit validation is handled on your own.  when maxlength has been exceeded 'overmax' class added to element
        };

      if ($.isFunction(options) && !callback) {
        callback = options;
        options = {};
      }
      options = $.extend(defaults, options);


      /**
      * Return the byte count of the specified character in UTF8 encoding.
      * Note: This won't cover UTF-8 characters that are 4 bytes long.
      *
      * @param input
      * @return {number}
      */
      function utf8CharByteCount(character) {
        var c = character.charCodeAt();
        // Not c then 0, else c < 128 then 1, else c < 2048 then 2, else 3
        return !c ? 0 : c < 128 ? 1 : c < 2048 ? 2 : 3;
      }

      /**
      * Return the length of the specified input in UTF8 encoding.
      *
      * @param input
      * @return {number}
      */
      function utf8Length(string) {
        return string.split("")
          .map(utf8CharByteCount)
          // Prevent reduce from throwing an error if the string is empty.
          .concat(0)
          .reduce(function(sum, val) { return sum + val; });
      }

      /**
      * Return the length of the specified input.
      *
      * @param input
      * @return {number}
      */
      function inputLength(input) {
        var text = input.val();

        if (options.twoCharLinebreak) {
          // Count all line breaks as 2 characters
          text = text.replace(/\r(?!\n)|\n(?!\r)/g, '\r\n');
        } else {
          // Remove all double-character (\r\n) linebreaks, so they're counted only once.
          text = text.replace(new RegExp('\r?\n', 'g'), '\n');
        }

        var currentLength = 0;

        if (options.utf8) {
          currentLength = utf8Length(text);
        } else {
          currentLength = text.length;
        }
        return currentLength;
      }

      /**
      * Truncate the text of the specified input.
      *
      * @param input
      * @param limit
      */
      function truncateChars(input, maxlength) {
        var text = input.val();

        if (options.twoCharLinebreak) {
          text = text.replace(/\r(?!\n)|\n(?!\r)/g, '\r\n');

          if (text[text.length - 1] === '\n') {
            maxlength -= text.length % 2;
          }
        }

        if (options.utf8) {
          var indexedSize = text.split("").map(utf8CharByteCount);
          for (
            var removedBytes = 0,
                bytesPastMax = utf8Length(text) - maxlength
            ;removedBytes < bytesPastMax
            ;removedBytes += indexedSize.pop()
          );
          maxlength -= (maxlength - indexedSize.length);
        }

        input.val(text.substr(0, maxlength));
      }

      /**
       * Return true if the indicator should be showing up.
       *
       * @param input
       * @param threshold
       * @param maxlength
       * @return {number}
       */
      function charsLeftThreshold(input, threshold, maxlength) {
        var output = true;
        if (!options.alwaysShow && (maxlength - inputLength(input) > threshold)) {
          output = false;
        }
        return output;
      }

      /**
       * Returns how many chars are left to complete the fill up of the form.
       *
       * @param input
       * @param maxlength
       * @return {number}
       */
      function remainingChars(input, maxlength) {
        var length = maxlength - inputLength(input);
        return length;
      }

      /**
       * When called displays the indicator.
       *
       * @param indicator
       */
      function showRemaining(currentInput, indicator) {
        indicator.css({
          display: 'block'
        });
        currentInput.trigger('maxlength.shown');
      }

      /**
       * When called shows the indicator.
       *
       * @param indicator
       */
      function hideRemaining(currentInput, indicator) {

        if (options.alwaysShow) {
          return;
        }

        indicator.css({
          display: 'none'
        });
        currentInput.trigger('maxlength.hidden');
      }

      /**
      * This function updates the value in the indicator
      *
      * @param maxLengthThisInput
      * @param typedChars
      * @return String
      */
      function updateMaxLengthHTML(currentInputText, maxLengthThisInput, typedChars) {
        var output = '';
        if (options.message) {
          if (typeof options.message === 'function') {
            output = options.message(currentInputText, maxLengthThisInput);
          } else {
            output = options.message.replace('%charsTyped%', typedChars)
              .replace('%charsRemaining%', maxLengthThisInput - typedChars)
              .replace('%charsTotal%', maxLengthThisInput);
          }
        } else {
          if (options.preText) {
            output += options.preText;
          }
          if (!options.showCharsTyped) {
            output += maxLengthThisInput - typedChars;
          }
          else {
            output += typedChars;
          }
          if (options.showMaxLength) {
            output += options.separator + maxLengthThisInput;
          }
          if (options.postText) {
            output += options.postText;
          }
        }
        return output;
      }

      /**
       * This function updates the value of the counter in the indicator.
       * Wants as parameters: the number of remaining chars, the element currently managed,
       * the maxLength for the current input and the indicator generated for it.
       *
       * @param remaining
       * @param currentInput
       * @param maxLengthCurrentInput
       * @param maxLengthIndicator
       */
      function manageRemainingVisibility(remaining, currentInput, maxLengthCurrentInput, maxLengthIndicator) {
        if (maxLengthIndicator) {
          maxLengthIndicator.html(updateMaxLengthHTML(currentInput.val(), maxLengthCurrentInput, (maxLengthCurrentInput - remaining)));

          if (remaining > 0) {
            if (charsLeftThreshold(currentInput, options.threshold, maxLengthCurrentInput)) {
              showRemaining(currentInput, maxLengthIndicator.removeClass(options.limitReachedClass).addClass(options.warningClass));
            } else {
              hideRemaining(currentInput, maxLengthIndicator);
            }
          } else {
            showRemaining(currentInput, maxLengthIndicator.removeClass(options.warningClass).addClass(options.limitReachedClass));
          }
        }

        if (options.customMaxAttribute) {
          // class to use for form validation on custom maxlength attribute
          if (remaining < 0) {
            currentInput.addClass('overmax');
          } else {
            currentInput.removeClass('overmax');
          }
        }
      }

      /**
       * This function returns an object containing all the
       * informations about the position of the current input
       *
       * @param currentInput
       * @return object {bottom height left right top width}
       *
       */
      function getPosition(currentInput) {
        var el = currentInput[0];
        return $.extend({}, (typeof el.getBoundingClientRect === 'function') ? el.getBoundingClientRect() : {
          width: el.offsetWidth,
          height: el.offsetHeight
        }, currentInput.offset());
      }

      /**
       * This function places the maxLengthIndicator based on placement config object.
       *
       * @param {object} placement
       * @param {$} maxLengthIndicator
       * @return null
       *
       */
      function placeWithCSS(placement, maxLengthIndicator) {
        if (!placement || !maxLengthIndicator){
          return;
        }

        var POSITION_KEYS = [
          'top',
          'bottom',
          'left',
          'right',
          'position'
        ];

        var cssPos = {};

        // filter css properties to position
        $.each(POSITION_KEYS, function (i, key) {
          var val = options.placement[key];
          if (typeof val !== 'undefined'){
            cssPos[key] = val;
          }
        });

        maxLengthIndicator.css(cssPos);

        return;
      }


      /**
       * This function places the maxLengthIndicator at the
       * top / bottom / left / right of the currentInput
       *
       * @param currentInput
       * @param maxLengthIndicator
       * @return null
       *
       */
      function place(currentInput, maxLengthIndicator) {
        var pos = getPosition(currentInput);

        // Supports custom placement handler
        if ($.type(options.placement) === 'function'){
          options.placement(currentInput, maxLengthIndicator, pos);
          return;
        }

        // Supports custom placement via css positional properties
        if ($.isPlainObject(options.placement)){
          placeWithCSS(options.placement, maxLengthIndicator);
          return;
        }

        var inputOuter = currentInput.outerWidth(),
          outerWidth = maxLengthIndicator.outerWidth(),
          actualWidth = maxLengthIndicator.width(),
          actualHeight = maxLengthIndicator.height();

        // get the right position if the indicator is appended to the input's parent
        if (options.appendToParent) {
          pos.top -= currentInput.parent().offset().top;
          pos.left -= currentInput.parent().offset().left;
        }

        switch (options.placement) {
          case 'bottom':
            maxLengthIndicator.css({ top: pos.top + pos.height, left: pos.left + pos.width / 2 - actualWidth / 2 });
            break;
          case 'top':
            maxLengthIndicator.css({ top: pos.top - actualHeight, left: pos.left + pos.width / 2 - actualWidth / 2 });
            break;
          case 'left':
            maxLengthIndicator.css({ top: pos.top + pos.height / 2 - actualHeight / 2, left: pos.left - actualWidth });
            break;
          case 'right':
            maxLengthIndicator.css({ top: pos.top + pos.height / 2 - actualHeight / 2, left: pos.left + pos.width });
            break;
          case 'bottom-right':
            maxLengthIndicator.css({ top: pos.top + pos.height, left: pos.left + pos.width });
            break;
          case 'top-right':
            maxLengthIndicator.css({ top: pos.top - actualHeight, left: pos.left + inputOuter });
            break;
          case 'top-left':
            maxLengthIndicator.css({ top: pos.top - actualHeight, left: pos.left - outerWidth });
            break;
          case 'bottom-left':
            maxLengthIndicator.css({ top: pos.top + currentInput.outerHeight(), left: pos.left - outerWidth });
            break;
          case 'centered-right':
            maxLengthIndicator.css({ top: pos.top + (actualHeight / 2), left: pos.left + inputOuter - outerWidth - 3 });
            break;

            // Some more options for placements
          case 'bottom-right-inside':
            maxLengthIndicator.css({ top: pos.top + pos.height, left: pos.left + pos.width - outerWidth });
            break;
          case 'top-right-inside':
            maxLengthIndicator.css({ top: pos.top - actualHeight, left: pos.left + inputOuter - outerWidth });
            break;
          case 'top-left-inside':
            maxLengthIndicator.css({ top: pos.top - actualHeight, left: pos.left });
            break;
          case 'bottom-left-inside':
            maxLengthIndicator.css({ top: pos.top + currentInput.outerHeight(), left: pos.left });
            break;
        }
      }

      /**
       * This function returns true if the indicator position needs to
       * be recalculated when the currentInput changes
       *
       * @return {boolean}
       *
       */
      function isPlacementMutable() {
        return options.placement === 'bottom-right-inside' || options.placement === 'top-right-inside' || typeof options.placement === 'function' || (options.message && typeof options.message === 'function');
      }

      /**
       * This function retrieves the maximum length of currentInput
       *
       * @param currentInput
       * @return {number}
       *
       */
      function getMaxLength(currentInput) {
        var max = currentInput.attr('maxlength') || options.customMaxAttribute;

        if (options.customMaxAttribute && !options.allowOverMax) {
          var custom = currentInput.attr(options.customMaxAttribute);
          if (!max || custom < max) {
            max = custom;
          }
        }

        if (!max) {
          max = currentInput.attr('size');
        }
        return max;
      }

      return this.each(function () {

        var currentInput = $(this),
          maxLengthCurrentInput,
          maxLengthIndicator;

        $(window).resize(function () {
          if (maxLengthIndicator) {
            place(currentInput, maxLengthIndicator);
          }
        });

        function firstInit() {
          var maxlengthContent = updateMaxLengthHTML(currentInput.val(), maxLengthCurrentInput, '0');
          maxLengthCurrentInput = getMaxLength(currentInput);

          if (!maxLengthIndicator) {
            maxLengthIndicator = $('<span class="bootstrap-maxlength"></span>').css({
              display: 'none',
              position: 'absolute',
              whiteSpace: 'nowrap',
              zIndex: 1099
            }).html(maxlengthContent);
          }

          // We need to detect resizes if we are dealing with a textarea:
          if (currentInput.is('textarea')) {
            currentInput.data('maxlenghtsizex', currentInput.outerWidth());
            currentInput.data('maxlenghtsizey', currentInput.outerHeight());

            currentInput.mouseup(function () {
              if (currentInput.outerWidth() !== currentInput.data('maxlenghtsizex') || currentInput.outerHeight() !== currentInput.data('maxlenghtsizey')) {
                place(currentInput, maxLengthIndicator);
              }

              currentInput.data('maxlenghtsizex', currentInput.outerWidth());
              currentInput.data('maxlenghtsizey', currentInput.outerHeight());
            });
          }

          if (options.appendToParent) {
            currentInput.parent().append(maxLengthIndicator);
            currentInput.parent().css('position', 'relative');
          } else {
            documentBody.append(maxLengthIndicator);
          }

          var remaining = remainingChars(currentInput, getMaxLength(currentInput));
          manageRemainingVisibility(remaining, currentInput, maxLengthCurrentInput, maxLengthIndicator);
          place(currentInput, maxLengthIndicator);
        }

        if (options.showOnReady) {
          currentInput.ready(function () {
            firstInit();
          });
        } else {
          currentInput.focus(function () {
            firstInit();
          });
        }

        currentInput.on('maxlength.reposition', function () {
          place(currentInput, maxLengthIndicator);
        });


        currentInput.on('destroyed', function () {
          if (maxLengthIndicator) {
            maxLengthIndicator.remove();
          }
        });

        currentInput.on('blur', function () {
          if (maxLengthIndicator && !options.showOnReady) {
            maxLengthIndicator.remove();
          }
        });

        currentInput.on('input', function () {
          var maxlength = getMaxLength(currentInput),
            remaining = remainingChars(currentInput, maxlength),
            output = true;

          if (options.validate && remaining < 0) {
            truncateChars(currentInput, maxlength);
            output = false;
          } else {
            manageRemainingVisibility(remaining, currentInput, maxLengthCurrentInput, maxLengthIndicator);
          }

          if (isPlacementMutable()) {
            place(currentInput, maxLengthIndicator);
          }

          return output;
        });
      });
    }
  });
}(jQuery));