diff --git a/src/static/js/scroll.js b/src/static/js/scroll.js
index 064831fe7..063e55513 100644
--- a/src/static/js/scroll.js
+++ b/src/static/js/scroll.js
@@ -1,3 +1,5 @@
+'use strict';
+
 /*
   This file handles scroll on edition or when user presses arrow keys.
   In this file we have two representations of line (browser and rep line).
@@ -17,23 +19,26 @@ function Scroll(outerWin) {
   this.rootDocument = parent.parent.document;
 }
 
-Scroll.prototype.scrollWhenCaretIsInTheLastLineOfViewportWhenNecessary = function (rep, isScrollableEvent, innerHeight) {
+Scroll.prototype.scrollWhenCaretIsInTheLastLineOfViewportWhenNecessary =
+  function (rep, isScrollableEvent, innerHeight) {
   // are we placing the caret on the line at the bottom of viewport?
   // And if so, do we need to scroll the editor, as defined on the settings.json?
-  const shouldScrollWhenCaretIsAtBottomOfViewport = this.scrollSettings.scrollWhenCaretIsInTheLastLineOfViewport;
-  if (shouldScrollWhenCaretIsAtBottomOfViewport) {
-    // avoid scrolling when selection includes multiple lines -- user can potentially be selecting more lines
-    // than it fits on viewport
-    const multipleLinesSelected = rep.selStart[0] !== rep.selEnd[0];
+    const shouldScrollWhenCaretIsAtBottomOfViewport =
+      this.scrollSettings.scrollWhenCaretIsInTheLastLineOfViewport;
+    if (shouldScrollWhenCaretIsAtBottomOfViewport) {
+      // avoid scrolling when selection includes multiple lines --
+      // user can potentially be selecting more lines
+      // than it fits on viewport
+      const multipleLinesSelected = rep.selStart[0] !== rep.selEnd[0];
 
-    // avoid scrolling when pad loads
-    if (isScrollableEvent && !multipleLinesSelected && this._isCaretAtTheBottomOfViewport(rep)) {
-      // when scrollWhenFocusLineIsOutOfViewport.percentage is 0, pixelsToScroll is 0
-      const pixelsToScroll = this._getPixelsRelativeToPercentageOfViewport(innerHeight);
-      this._scrollYPage(pixelsToScroll);
+      // avoid scrolling when pad loads
+      if (isScrollableEvent && !multipleLinesSelected && this._isCaretAtTheBottomOfViewport(rep)) {
+        // when scrollWhenFocusLineIsOutOfViewport.percentage is 0, pixelsToScroll is 0
+        const pixelsToScroll = this._getPixelsRelativeToPercentageOfViewport(innerHeight);
+        this._scrollYPage(pixelsToScroll);
+      }
     }
-  }
-};
+  };
 
 Scroll.prototype.scrollWhenPressArrowKeys = function (arrowUp, rep, innerHeight) {
   // if percentageScrollArrowUp is 0, let the scroll to be handled as default, put the previous
@@ -60,8 +65,10 @@ Scroll.prototype._isCaretAtTheBottomOfViewport = function (rep) {
   const caretLine = rep.selStart[0];
   const lineAfterCaretLine = caretLine + 1;
   const firstLineVisibleAfterCaretLine = caretPosition.getNextVisibleLine(lineAfterCaretLine, rep);
-  const caretLineIsPartiallyVisibleOnViewport = this._isLinePartiallyVisibleOnViewport(caretLine, rep);
-  const lineAfterCaretLineIsPartiallyVisibleOnViewport = this._isLinePartiallyVisibleOnViewport(firstLineVisibleAfterCaretLine, rep);
+  const caretLineIsPartiallyVisibleOnViewport =
+    this._isLinePartiallyVisibleOnViewport(caretLine, rep);
+  const lineAfterCaretLineIsPartiallyVisibleOnViewport =
+    this._isLinePartiallyVisibleOnViewport(firstLineVisibleAfterCaretLine, rep);
   if (caretLineIsPartiallyVisibleOnViewport || lineAfterCaretLineIsPartiallyVisibleOnViewport) {
     // check if the caret is in the bottom of the viewport
     const caretLinePosition = caretPosition.getPosition();
@@ -99,9 +106,11 @@ Scroll.prototype._getViewPortTopBottom = function () {
   const doc = this.doc;
   const height = doc.documentElement.clientHeight; // includes padding
 
-  // we have to get the exactly height of the viewport. So it has to subtract all the values which changes
+  // we have to get the exactly height of the viewport.
+  // So it has to subtract all the values which changes
   // the viewport height (E.g. padding, position top)
-  const viewportExtraSpacesAndPosition = this._getEditorPositionTop() + this._getPaddingTopAddedWhenPageViewIsEnable();
+  const viewportExtraSpacesAndPosition =
+    this._getEditorPositionTop() + this._getPaddingTopAddedWhenPageViewIsEnable();
   return {
     top: theTop,
     bottom: (theTop + height - viewportExtraSpacesAndPosition),
@@ -162,9 +171,12 @@ Scroll.prototype.setScrollXY = function (x, y) {
 Scroll.prototype._isCaretAtTheTopOfViewport = function (rep) {
   const caretLine = rep.selStart[0];
   const linePrevCaretLine = caretLine - 1;
-  const firstLineVisibleBeforeCaretLine = caretPosition.getPreviousVisibleLine(linePrevCaretLine, rep);
-  const caretLineIsPartiallyVisibleOnViewport = this._isLinePartiallyVisibleOnViewport(caretLine, rep);
-  const lineBeforeCaretLineIsPartiallyVisibleOnViewport = this._isLinePartiallyVisibleOnViewport(firstLineVisibleBeforeCaretLine, rep);
+  const firstLineVisibleBeforeCaretLine =
+    caretPosition.getPreviousVisibleLine(linePrevCaretLine, rep);
+  const caretLineIsPartiallyVisibleOnViewport =
+    this._isLinePartiallyVisibleOnViewport(caretLine, rep);
+  const lineBeforeCaretLineIsPartiallyVisibleOnViewport =
+    this._isLinePartiallyVisibleOnViewport(firstLineVisibleBeforeCaretLine, rep);
   if (caretLineIsPartiallyVisibleOnViewport || lineBeforeCaretLineIsPartiallyVisibleOnViewport) {
     const caretLinePosition = caretPosition.getPosition(); // get the position of the browser line
     const viewportPosition = this._getViewPortTopBottom();
@@ -172,7 +184,8 @@ Scroll.prototype._isCaretAtTheTopOfViewport = function (rep) {
     const viewportBottom = viewportPosition.bottom;
     const caretLineIsBelowViewportTop = caretLinePosition.bottom >= viewportTop;
     const caretLineIsAboveViewportBottom = caretLinePosition.top < viewportBottom;
-    const caretLineIsInsideOfViewport = caretLineIsBelowViewportTop && caretLineIsAboveViewportBottom;
+    const caretLineIsInsideOfViewport =
+      caretLineIsBelowViewportTop && caretLineIsAboveViewportBottom;
     if (caretLineIsInsideOfViewport) {
       const prevLineTop = caretPosition.getPositionTopOfPreviousBrowserLine(caretLinePosition, rep);
       const previousLineIsAboveViewportTop = prevLineTop < viewportTop;
@@ -185,14 +198,15 @@ Scroll.prototype._isCaretAtTheTopOfViewport = function (rep) {
 // By default, when user makes an edition in a line out of viewport, this line goes
 // to the edge of viewport. This function gets the extra pixels necessary to get the
 // caret line in a position X relative to Y% viewport.
-Scroll.prototype._getPixelsRelativeToPercentageOfViewport = function (innerHeight, aboveOfViewport) {
-  let pixels = 0;
-  const scrollPercentageRelativeToViewport = this._getPercentageToScroll(aboveOfViewport);
-  if (scrollPercentageRelativeToViewport > 0 && scrollPercentageRelativeToViewport <= 1) {
-    pixels = parseInt(innerHeight * scrollPercentageRelativeToViewport);
-  }
-  return pixels;
-};
+Scroll.prototype._getPixelsRelativeToPercentageOfViewport =
+  function (innerHeight, aboveOfViewport) {
+    let pixels = 0;
+    const scrollPercentageRelativeToViewport = this._getPercentageToScroll(aboveOfViewport);
+    if (scrollPercentageRelativeToViewport > 0 && scrollPercentageRelativeToViewport <= 1) {
+      pixels = parseInt(innerHeight * scrollPercentageRelativeToViewport);
+    }
+    return pixels;
+  };
 
 // we use different percentages when change selection. It depends on if it is
 // either above the top or below the bottom of the page
@@ -226,30 +240,34 @@ Scroll.prototype._scrollYPageWithoutAnimation = function (pixelsToScroll) {
   this.outerWin.scrollBy(0, pixelsToScroll);
 };
 
-Scroll.prototype._scrollYPageWithAnimation = function (pixelsToScroll, durationOfAnimationToShowFocusline) {
-  const outerDocBody = this.doc.getElementById('outerdocbody');
+Scroll.prototype._scrollYPageWithAnimation =
+  function (pixelsToScroll, durationOfAnimationToShowFocusline) {
+    const outerDocBody = this.doc.getElementById('outerdocbody');
 
-  // it works on later versions of Chrome
-  const $outerDocBody = $(outerDocBody);
-  this._triggerScrollWithAnimation($outerDocBody, pixelsToScroll, durationOfAnimationToShowFocusline);
+    // it works on later versions of Chrome
+    const $outerDocBody = $(outerDocBody);
+    this._triggerScrollWithAnimation(
+        $outerDocBody, pixelsToScroll, durationOfAnimationToShowFocusline);
 
-  // it works on Firefox and earlier versions of Chrome
-  const $outerDocBodyParent = $outerDocBody.parent();
-  this._triggerScrollWithAnimation($outerDocBodyParent, pixelsToScroll, durationOfAnimationToShowFocusline);
-};
+    // it works on Firefox and earlier versions of Chrome
+    const $outerDocBodyParent = $outerDocBody.parent();
+    this._triggerScrollWithAnimation(
+        $outerDocBodyParent, pixelsToScroll, durationOfAnimationToShowFocusline);
+  };
 
-// using a custom queue and clearing it, we avoid creating a queue of scroll animations. So if this function
-// is called twice quickly, only the last one runs.
-Scroll.prototype._triggerScrollWithAnimation = function ($elem, pixelsToScroll, durationOfAnimationToShowFocusline) {
-  // clear the queue of animation
-  $elem.stop('scrollanimation');
-  $elem.animate({
-    scrollTop: `+=${pixelsToScroll}`,
-  }, {
-    duration: durationOfAnimationToShowFocusline,
-    queue: 'scrollanimation',
-  }).dequeue('scrollanimation');
-};
+// using a custom queue and clearing it, we avoid creating a queue of scroll animations.
+// So if this function is called twice quickly, only the last one runs.
+Scroll.prototype._triggerScrollWithAnimation =
+  function ($elem, pixelsToScroll, durationOfAnimationToShowFocusline) {
+    // clear the queue of animation
+    $elem.stop('scrollanimation');
+    $elem.animate({
+      scrollTop: `+=${pixelsToScroll}`,
+    }, {
+      duration: durationOfAnimationToShowFocusline,
+      queue: 'scrollanimation',
+    }).dequeue('scrollanimation');
+  };
 
 // scrollAmountWhenFocusLineIsOutOfViewport is set to 0 (default), scroll it the minimum distance
 // needed to be completely in view. If the value is greater than 0 and less than or equal to 1,
@@ -257,7 +275,6 @@ Scroll.prototype._triggerScrollWithAnimation = function ($elem, pixelsToScroll,
 // (viewport height * scrollAmountWhenFocusLineIsOutOfViewport) pixels
 Scroll.prototype.scrollNodeVerticallyIntoView = function (rep, innerHeight) {
   const viewport = this._getViewPortTopBottom();
-  const isPartOfRepLineOutOfViewport = this._partOfRepLineIsOutOfViewport(viewport, rep);
 
   // when the selection changes outside of the viewport the browser automatically scrolls the line
   // to inside of the viewport. Tested on IE, Firefox, Chrome in releases from 2015 until now
@@ -269,10 +286,12 @@ Scroll.prototype.scrollNodeVerticallyIntoView = function (rep, innerHeight) {
     const caretIsAboveOfViewport = distanceOfTopOfViewport < 0;
     const caretIsBelowOfViewport = distanceOfBottomOfViewport < 0;
     if (caretIsAboveOfViewport) {
-      var pixelsToScroll = distanceOfTopOfViewport - this._getPixelsRelativeToPercentageOfViewport(innerHeight, true);
+      const pixelsToScroll =
+        distanceOfTopOfViewport - this._getPixelsRelativeToPercentageOfViewport(innerHeight, true);
       this._scrollYPage(pixelsToScroll);
     } else if (caretIsBelowOfViewport) {
-      var pixelsToScroll = -distanceOfBottomOfViewport + this._getPixelsRelativeToPercentageOfViewport(innerHeight);
+      const pixelsToScroll = -distanceOfBottomOfViewport +
+        this._getPixelsRelativeToPercentageOfViewport(innerHeight);
       this._scrollYPage(pixelsToScroll);
     } else {
       this.scrollWhenCaretIsInTheLastLineOfViewportWhenNecessary(rep, true, innerHeight);
@@ -311,12 +330,10 @@ Scroll.prototype.getVisibleLineRange = function (rep) {
   const obj = {};
   const self = this;
   const start = rep.lines.search((e) => self._getLineEntryTopBottom(e, obj).bottom > viewport.top);
-  let end = rep.lines.search((e) =>
-    // return the first line that the top position is greater or equal than
-    // the viewport. That is the first line that is below the viewport bottom.
-    // So the line that is in the bottom of the viewport is the very previous one.
-    self._getLineEntryTopBottom(e, obj).top >= viewport.bottom
-  );
+  // return the first line that the top position is greater or equal than
+  // the viewport. That is the first line that is below the viewport bottom.
+  // So the line that is in the bottom of the viewport is the very previous one.
+  let end = rep.lines.search((e) => self._getLineEntryTopBottom(e, obj).top >= viewport.bottom);
   if (end < start) end = start; // unlikely
   // top.console.log(start+","+(end -1));
   return [start, end - 1];
@@ -327,6 +344,4 @@ Scroll.prototype.getVisibleCharRange = function (rep) {
   return [rep.lines.offsetOfIndex(lineRange[0]), rep.lines.offsetOfIndex(lineRange[1])];
 };
 
-exports.init = function (outerWin) {
-  return new Scroll(outerWin);
-};
+exports.init = (outerWin) => new Scroll(outerWin);