diff --git a/wagtail_modeltranslation/static/wagtail_modeltranslation/js/copy_stream_fields.js b/wagtail_modeltranslation/static/wagtail_modeltranslation/js/copy_stream_fields.js
index 4890846..020a493 100644
--- a/wagtail_modeltranslation/static/wagtail_modeltranslation/js/copy_stream_fields.js
+++ b/wagtail_modeltranslation/static/wagtail_modeltranslation/js/copy_stream_fields.js
@@ -17,27 +17,27 @@ $(document).ready(function(){
       // Wagtail < 2.6 
       header = $(currentStreamField).children('h2')[0];
       //Search for the input field so that we can get is id to know the field's name.
-      let streamFieldDiv = $(currentStreamField).find('div.sequence-container.sequence-type-stream')[0];
-      let fieldInfos = $(streamFieldDiv).find('input')[0].id.split('-')[0];
-      let lastUnderscore = fieldInfos.lastIndexOf("_");
+      var streamFieldDiv = $(currentStreamField).find('div.sequence-container.sequence-type-stream')[0];
+      var fieldInfos = $(streamFieldDiv).find('input')[0].id.split('-')[0];
+      var lastUnderscore = fieldInfos.lastIndexOf("_");
       fieldName = fieldInfos.substring(0, lastUnderscore);
       fieldLang = fieldInfos.substring(lastUnderscore + 1, fieldInfos.length);
     } else if(versionCompare(WAGTAIL_VERSION,'2.7.0', {zeroExtend: true})===-1){
       // Wagtail < 2.7 
       header = $(currentStreamField).children('.title-wrapper')[0];
       //Search for the input field so that we can get is id to know the field's name.
-      let streamFieldDiv = $(currentStreamField).find('div.sequence-container.sequence-type-stream')[0];
-      let fieldInfos = $(streamFieldDiv).find('input')[0].id.split('-')[0];
-      let lastUnderscore = fieldInfos.lastIndexOf("_");
+      var streamFieldDiv = $(currentStreamField).find('div.sequence-container.sequence-type-stream')[0];
+      var fieldInfos = $(streamFieldDiv).find('input')[0].id.split('-')[0];
+      var lastUnderscore = fieldInfos.lastIndexOf("_");
       fieldName = fieldInfos.substring(0, lastUnderscore);
       fieldLang = fieldInfos.substring(lastUnderscore + 1, fieldInfos.length);
     } else {
       // Wagtail >= 2.7 
       header = $(currentStreamField).children('.title-wrapper')[0];
       //Search for the input field so that we can get is id to know the field's name.
-      let streamFieldDiv = $(currentStreamField).find('.field-content')[0];
-      let fieldInfos = $(streamFieldDiv).find('input')[0].id.split('-')[0];
-      let lastUnderscore = fieldInfos.lastIndexOf("_");
+      var streamFieldDiv = $(currentStreamField).find('.field-content')[0];
+      var fieldInfos = $(streamFieldDiv).find('input')[0].id.split('-')[0];
+      var lastUnderscore = fieldInfos.lastIndexOf("_");
       fieldName = fieldInfos.substring(0, lastUnderscore);
       fieldLang = fieldInfos.substring(lastUnderscore + 1, fieldInfos.length);
     }
@@ -47,7 +47,7 @@ $(document).ready(function(){
 			if (fieldLang != langs[j]) {
 				var currentFieldID = fieldName + '_' + fieldLang;
 				var targetFieldID = fieldName + '_' + langs [j];
-				$(header).children('.translation-field-copy-wrapper')[0].innerHTML += `<button class="button translation-field-copy" current-lang-code="${currentFieldID}" data-lang-code="${targetFieldID}">${langs[j]}</button>`;
+				$(header).children('.translation-field-copy-wrapper')[0].innerHTML += '<button class="button translation-field-copy" current-lang-code="' + currentFieldID + '" data-lang-code="' + targetFieldID + '">' + langs[j] + '</button>';
 			};
 		};
 	};
@@ -80,11 +80,11 @@ function requestCopyField(originID, targetID) {
 	})
 	.done(function(data) {
 		/* Put the html data in the targetID field */
-		var wrapperDiv = $(`#${targetID}-count`).parents('.input')[0];
+		var wrapperDiv = $('#' + targetID + '-count').parents('.input')[0];
 		$(wrapperDiv).html(data);
 	})
 	.fail(function(error) {
-		console.log(`wagtail-modeltranslation error: ${error.responseText}`);
+		console.log('wagtail-modeltranslation error: ' + error.responseText);
 	})
 
 }
diff --git a/wagtail_modeltranslation/static/wagtail_modeltranslation/js/version_compare.js b/wagtail_modeltranslation/static/wagtail_modeltranslation/js/version_compare.js
index 77ef581..55a4a04 100644
--- a/wagtail_modeltranslation/static/wagtail_modeltranslation/js/version_compare.js
+++ b/wagtail_modeltranslation/static/wagtail_modeltranslation/js/version_compare.js
@@ -5,15 +5,17 @@
  *
  * @param {string} v1 The first version to be compared.
  * @param {string} v2 The second version to be compared.
- * @param {object} [options] Optional flags that affect comparison behavior:
+ * @param {object} [options] Optional flags that affect comparison behavior.
+ * @param {boolean} [options.lexicographical = false] Switch to compare version strings lexicographically instead of naturally.
+ * @param {boolean} [options.zeroExtend = false] Switch to pad version with "zero" parts instead to be considered smaller.
  * <ul>
  *     <li>
- *         <tt>lexicographical: false</tt> compares each part of the version strings lexicographically instead of
+ *         <tt>lexicographical: true</tt> compares each part of the version strings lexicographically instead of
  *         naturally; this allows suffixes such as "b" or "dev" but will cause "1.10" to be considered smaller than
  *         "1.2".
  *     </li>
  *     <li>
- *         <tt>zeroExtend: false</tt> changes the result if one version string has less parts than the other. In
+ *         <tt>zeroExtend: true</tt> changes the result if one version string has less parts than the other. In
  *         this case the shorter string will be padded with "zero" parts instead of being considered smaller.
  *     </li>
  * </ul>