MDL-57972 javascript: Change truncate.js behaviour

Updated truncate.js to behave closer to the moodle implementation of
shorten_text.

Part of MDL-55611

lib/amd/src/truncate.js

@@ -23,6 +23,8 @@
  * @package    core
  * @class      truncate
  * @copyright  2017 Pathable
+ *             2017 Mathias Bynens
+ *             2017 Ryan Wyllie <ryan@moodle.com>
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 define(['jquery'], function($) {
@@ -33,6 +35,74 @@ define(['jquery'], function($) {
   // Matches the first word in the string.
   var start = /^(\S*)/;
 
+  // Matches any space characters.
+  var space = /\s/;
+
+  // Special thanks to Mathias Bynens for the multi-byte char
+  // implementation. Much love.
+  // see: https://github.com/mathiasbynens/String.prototype.at/blob/master/at.js
+  var charLengthAt = function(text, position) {
+    if (this == null) {
+      throw TypeError();
+    }
+    var string = String(text);
+    var size = string.length;
+    // `ToInteger`
+    var index = position ? Number(position) : 0;
+    if (index != index) { // better `isNaN`
+      index = 0;
+    }
+    // Account for out-of-bounds indices
+    // The odd lower bound is because the ToInteger operation is
+    // going to round `n` to `0` for `-1 < n <= 0`.
+    if (index <= -1 || index >= size) {
+      return '';
+    }
+    // Second half of `ToInteger`
+    index = index | 0;
+    // Get the first code unit and code unit value
+    var cuFirst = string.charCodeAt(index);
+    var cuSecond;
+    var nextIndex = index + 1;
+    var len = 1;
+    if ( // Check if it’s the start of a surrogate pair.
+      cuFirst >= 0xD800 && cuFirst <= 0xDBFF && // high surrogate
+      size > nextIndex // there is a next code unit
+    ) {
+      cuSecond = string.charCodeAt(nextIndex);
+      if (cuSecond >= 0xDC00 && cuSecond <= 0xDFFF) { // low surrogate
+        len = 2;
+      }
+    }
+    return len;
+  };
+
+  var lengthMultiByte = function(text) {
+    var count = 0;
+
+    for (var i = 0; i < text.length; i += charLengthAt(text, i)) {
+      count++;
+    }
+
+    return count;
+  };
+
+  var getSliceLength = function(text, amount) {
+    if (!text.length) {
+      return 0;
+    }
+
+    var length = 0;
+    var count = 0;
+
+    do {
+      length += charLengthAt(text, length);
+      count++;
+    } while (length < text.length && count < amount);
+
+    return length;
+  };
+
   // Return a truncated html string.  Delegates to $.fn.truncate.
   $.truncate = function(html, options) {
     return $('<div></div>').append(html).truncate(options).html();
@@ -48,29 +118,42 @@ define(['jquery'], function($) {
 
       if (o.noBreaks) self.find('br').replaceWith(' ');
 
+      var ellipsisLength = o.ellipsis.length;
       var text = self.text();
-      var excess = text.length - o.length;
+      var textLength = lengthMultiByte(text);
+      var excess = textLength - o.length + ellipsisLength;
 
+      if (textLength < o.length) return;
       if (o.stripTags) self.text(text);
 
       // Chop off any partial words if appropriate.
       if (o.words && excess > 0) {
-        var truncated = text.slice(0, o.length).replace(chop, '').length;
+        var sliced = text.slice(0, getSliceLength(text, o.length - ellipsisLength) + 1);
+        var replaced = sliced.replace(chop, '');
+        var truncated = lengthMultiByte(replaced);
+        var oneWord = sliced.match(space) ? false : true;
 
         if (o.keepFirstWord && truncated === 0) {
-          excess = text.length - start.exec(text)[0].length - 1;
+          excess = textLength - lengthMultiByte(start.exec(text)[0]) - ellipsisLength;
+        } else if (oneWord && truncated === 0) {
+          excess = textLength - o.length + ellipsisLength;
         } else {
-          excess = text.length - truncated - 1;
+          excess = textLength - truncated - 1;
         }
       }
 
+      // The requested length is larger than the text. No need for ellipsis.
+      if (excess > textLength) {
+        excess = textLength - o.length;
+      }
+
       if (excess < 0 || !excess && !o.truncated) return;
 
       // Iterate over each child node in reverse, removing excess text.
       $.each(self.contents().get().reverse(), function(i, el) {
         var $el = $(el);
         var text = $el.text();
-        var length = text.length;
+        var length = lengthMultiByte(text);
 
         // If the text is longer than the excess, remove the node and continue.
         if (length <= excess) {
@@ -82,12 +165,14 @@ define(['jquery'], function($) {
 
         // Remove the excess text and append the ellipsis.
         if (el.nodeType === 3) {
-          $(el.splitText(length - excess - 1)).replaceWith(o.ellipsis);
+          var splitAmount = length - excess;
+          splitAmount = splitAmount >= 0 ? getSliceLength(text, splitAmount) : 0;
+          $(el.splitText(splitAmount)).replaceWith(o.ellipsis);
           return false;
         }
 
         // Recursively truncate child nodes.
-        $el.truncate($.extend(o, {length: length - excess}));
+        $el.truncate($.extend(o, {length: length - excess + ellipsisLength}));
         return false;
       });
     });
@@ -115,6 +200,7 @@ define(['jquery'], function($) {
     // used to prevent a hanging ellipsis, but displays incorrectly in Chrome
     // on Windows 7.
     // http://code.google.com/p/chromium/issues/detail?id=68323
+    //ellipsis: '\u2026' // '\u2060\u2026'
     ellipsis: '\u2026' // '\u2060\u2026'
 
   };