Adding info about ESLint in README.md

This includes:

+ Removing trailling whitespaces
+ Adding missing const keywords
+ Fixing equality checks
+ Removing unused variables, functions, etc...
+ Adding missing let & const statements
+ Use strict
+ Correcting all names to use camelCase
+ Using semicolons everywhere
+ Use Allman style everywhere
+ Make comments headers uniform

This also includes:

+ Fixing displayed version number

.gitignore

@@ -1,2 +1,6 @@
+# ESLINT report
+eslint_report.html
+
+# Demo sources
 demos/src_highres
 demos/src_lowres

README.md

@@ -25,16 +25,19 @@ flowchart TB
 ```
 
 Melpomene is mainly one JS file and one CSS file. You only need to include them in you web page. They are :
-    + `melpomene.js`
-    + `melpomene.css`
+
++ `melpomene.js`
+
++ `melpomene.css`
 
 The JS files expect you to write some very specific HTML tags to be able to work.
 To simplify things, you only need to copy-paste the content of `melpomene.html` into your own page and change a few things :
+
 + You must duplicate the `img` tag for each of you comic page and :
     + set `url` to the actual URL of your page
     + set `height` and `width` to the actual image sizes 
     + set `data-zooms` with the zooms information, like so : `<zoom 1 width>, <zoom 1 height>, <zoom 1 x offset>, <zoom 1 y offset>; <zoom 2 width> ...`
-        + example : `<img loading="lazy" src="https://www.peppercarrot.com/0_sources/ep35_The-Reflection/hi-res/en_Pepper-and-Carrot_by-David-Revoy_E35P01.jpg" data-zooms="2481.0,1327.1057,0.0,0.0;593.15338,1076.4635,0.0,1364.053;890.72864,491.29874,830.81415,1751.5;2481.0,1078.4192,0.0,1364.053;562.77032,909.44702,102.48115,2491.6567;920.74463,909.44702,698.55927,2491.6567;728.776,909.44702,1652.3695,2491.6567"/>`
+    + example : `<img loading="lazy" src="https://www.peppercarrot.com/0_sources/ep35_The-Reflection/hi-res/en_Pepper-and-Carrot_by-David-Revoy_E35P01.jpg" data-zooms="2481.0,1327.1057,0.0,0.0;593.15338,1076.4635,0.0,1364.053;890.72864,491.29874,830.81415,1751.5;2481.0,1078.4192,0.0,1364.053;562.77032,909.4470    2,102.48115,2491.6567;920.74463,909.44702,698.55927,2491.6567;728.776,909.44702,1652.3695,2491.6567"/>`
 
 Because doing this by hand would be very tedious, Melpomene comes with an helper script that allows generating that HTML for you from SVGs.
 
@@ -45,7 +48,7 @@ The following limitations are known and will be improved upon :
 + Mobile support is currently limited
 + There are some performences issues
 
-# How to setup Melpomene ?
+# How to use Melpomene ?
 
 ## Defining the zooms
 
@@ -61,12 +64,12 @@ To create the zooms for a comic page, what you need to do is :
      * If you want to change the zoom order, you can change their order in the layer view of your SVG tool if they support it
 3. Once you are done, save the SGV
 
-
 ## Generating the HTML files
 
 Once the SVG for your pages are done, put them in one folder. Then, you can run the zoom generator.
 
 You need to open a terminal and then run :
+
 + `python zooms_generator.py <path to the SVG folder> html -p <prefix of the img's url> -e <extension of the img's url>`
     + For example, if your comic pages are hosted at `static/comic/page_x.jpg`, the svg must be named `page_x.svg`
       and you must run `python zooms_generator.py <path to the SVG folder> html -p /static/comic/ -e jpg`
@@ -89,6 +92,24 @@ If you need to do some global scaling / offset of all zooms in HTML (if for exam
     + If they become greater than the page size, they get clamped to the page size and width / height get reduced to compensate
 + `data-global-zoom-scale="<float value>"` : scale all positions / sizes by this factor
 
+# Developpement
+
+## Setting up quality checking for JS
+
+ Regarding JS, quality checking is done using [eslint](https://eslint.org/).
+
+The configuration file is `eslint/eslintrc.json`.
+
+To setup eslint, you can either install it on your system reading it's documentation, or use the provided Dockerfile to run it. This requires [docker](https://www.docker.com/).
+
+To do so, assuming you are using linux, after installing docker, you can run from this repository root:
+
++ `docker build -t melpomene-eslint eslint/`, once
+
++ `docker run -v .:/melpomene:rw -w /melpomene --user $(id -u):$(id -g) melpomene-eslint`, every time you want to run the analysis
+
+You can now open `eslint_report.html` to see the result.
+
 # Credits
 
-Most examples and the documentation of Melpomene uses illustrations from David "Deevad" Revoy's "Pepper & Carrot" webcomic, which is published under CC-BY 4.0. Full licence [here](https://www.peppercarrot.com/en/license/index.html).
+Most examples and the documentation of Melpomene uses illustrations from David "Deevad" Revoy's "Pepper & Carrot" webcomic, which is published under CC-BY 4.0. Full licence [here](https://www.peppercarrot.com/en/license/index.html). 

eslint/Dockerfile

@@ -0,0 +1,11 @@
+FROM debian:latest
+
+RUN apt-get update && apt-get install -y --no-install-recommends npm
+
+RUN npm install eslint --global
+
+COPY eslintrc.json /eslintrc.json
+
+ENTRYPOINT ["eslint", "--no-eslintrc"]
+
+CMD ["--help"]

eslint/eslintrc.json

@@ -0,0 +1,34 @@
+{
+    "env": {
+        "browser": true,
+	"es2021": true
+    },
+    "extends": [
+        "eslint:all"
+    ],
+    "rules": {
+        "semi": "warn",
+        "spaced-comment": "warn",
+        "padded-blocks": ["warn", "never"],
+        "camelcase": "warn",
+        "multiline-comment-style": "off",
+        "max-len": "warn",
+        "prefer-template": "warn",
+        "object-curly-spacing" : ["warn", "always"],
+        "func-style": ["warn", "declaration"],
+        "key-spacing": "warn",
+        "one-var": ["warn", "never"],
+        "quotes": "warn",
+        "space-before-function-paren": ["warn", "never"],
+        "no-undefined": "off",
+        "strict": ["error", "global"],
+        "keyword-spacing": "warn",
+        "function-call-argument-newline": "warn",
+        "operator-assignment": "off",
+        "space-before-blocks": "warn",
+        "brace-style": ["warn", "allman", {"allowSingleLine": true}],
+        "function-call-argument-newline" : ["warn", "consistent"],
+        "function-paren-newline": ["warn", "consistent"],
+        "no-magic-numbers": ["error", {"ignore": [0,1,2,100]}]
+    }
+}

melpomene.js

@@ -2,60 +2,63 @@
 /* Version 1.0.0_RC1 */
 /* CC-BY-NC-SA : https://git.aribaud.net/caribaud/melpomene/ */
 
-//============
+"use strict";
+
+// ============
 //   CONTROLS
-//============
+// ============
 
-MOVE_NEXT = "ArrowRight"
-MOVE_BACK = "ArrowLeft"
-TOGGLE_FULLSCREEN = "F"
-TOGGLE_PROGRESSBAR = "P"
-TOGGLE_VIEW_MODE = "V"
+const MOVE_NEXT = "ArrowRight";
+const MOVE_BACK = "ArrowLeft";
+const TOGGLE_FULLSCREEN = "F";
+const TOGGLE_PROGRESSBAR = "P";
+const TOGGLE_VIEW_MODE = "V";
 
 
-//========================
+// ========================
 //   NAVIGATION CONSTANTS
-//========================
+// ========================
 
-PAGE_TRANSITION_SPEED = "1.5s"
-MOUSEWHELL_MIN_DELAY = 50
-DELAY_BEFORE_HIDDING_CONTROLS = 4000;
+const MOUSEWHELL_MIN_DELAY = 50;
+const DELAY_BEFORE_HIDDING_CONTROLS = 4000;
 
-//====================
+// ====================
 //   STATES CONSTANTS
-//====================
+// ====================
 
-MELPOMENE_VERSION = "1.0.0_RC1"
+const MELPOMENE_VERSION = "1.0.0_UNSTABLE";
 
-READER_FRAME = document.getElementById("melpomene")
-READER_CONTENT_FRAME = document.getElementById("melpomene-content-frame")
-READER_PAGES = document.getElementById("melpomene-pages")
-FOCUS_OVERLAY_HEIGHT = document.getElementById("melpomene-focus")
-FOCUS_OVERLAY_WIDTH = document.getElementById("melpomene-focus-col")
-HELP_CONTROLS = document.getElementById("melpomene-help-menu")
-PROGRESS_BAR_CONTAINER = document.getElementById("melpomene-progress-container")
-PROGRESS_BAR = document.getElementById("melpomene-progress-bar")
-PROGRESS_BAR_PAGES = document.getElementById("melpomene-progress-sections")
-VERSION_DISPLAY = document.getElementById("melpomene-version")
+const READER_FRAME = document.getElementById("melpomene");
+const READER_CONTENT_FRAME = document.getElementById("melpomene-content-frame");
+const READER_PAGES = document.getElementById("melpomene-pages");
+const FOCUS_OVERLAY_HEIGHT = document.getElementById("melpomene-focus");
+const FOCUS_OVERLAY_WIDTH = document.getElementById("melpomene-focus-col");
+const HELP_CONTROLS = document.getElementById("melpomene-help-menu");
+const PROGRESS_BAR_CONTAINER = document.getElementById("melpomene-progress-container");
+const PROGRESS_BAR = document.getElementById("melpomene-progress-bar");
+const PROGRESS_BAR_PAGES = document.getElementById("melpomene-progress-sections");
+const VERSION_DISPLAY = document.getElementById("melpomene-version");
 
-//===========================
+// ===========================
 //   STATES GLOBAL VARIABLES
-//===========================
+// ===========================
 
+var PAGES_ZOOMS;
 // The variable ZOOMS can either be defined by another JS file or contructed at init
-if (typeof PAGES_ZOOMS == 'undefined') {
-    PAGES_ZOOMS = null
+if (typeof PAGES_ZOOMS === 'undefined')
+{
+    PAGES_ZOOMS = null;
 }
 
-CURRENT_ZOOM = 0
-CURRENT_PAGE = 1
-CURRENT_WIDTH = 0
-CURRENT_HEIGHT = 0
-CURRENT_X = 0
-CURRENT_Y = 0
+var CURRENT_ZOOM = 0;
+var CURRENT_PAGE = 1;
+var CURRENT_WIDTH = 0;
+var CURRENT_HEIGHT = 0;
+var CURRENT_X = 0;
+var CURRENT_Y = 0;
 
-IS_PAGE_MODE = false
-MOUSEWHELL_WAIT = false
+var IS_PAGE_MODE = false;
+var MOUSEWHELL_WAIT = false;
 
 // =============
 //   UTILITIES
@@ -64,360 +67,433 @@ MOUSEWHELL_WAIT = false
 // Zooms utilites
 // --------------
 
-function globalZoomScale(){
-    
-    if (READER_PAGES.dataset.globalZoomScale != undefined){
-        return parseFloat(READER_PAGES.dataset.globalZoomScale)
+function globalZoomScale()
+{
+    if (READER_PAGES.dataset.globalZoomScale !== undefined)
+    {
+        return parseFloat(READER_PAGES.dataset.globalZoomScale);
     }
 
-    return 1.0
+    return 1.0;
 }
 
-function globalZoomOffsetX(){
-    
-    if (READER_PAGES.dataset.globalZoomOffset != undefined){
-        return parseFloat(READER_PAGES.dataset.globalZoomOffset.split(',')[0])
+function globalZoomOffsetX()
+{
+    if (READER_PAGES.dataset.globalZoomOffset !== undefined)
+    {
+        return parseFloat(READER_PAGES.dataset.globalZoomOffset.split(',')[0]);
     }
 
-    return 0.0
+    return 0.0;
 }
 
-function globalZoomOffsetY(){
-    
-    if (READER_PAGES.dataset.globalZoomOffset != undefined){
-        return parseFloat(READER_PAGES.dataset.globalZoomOffset.split(',')[1])
+function globalZoomOffsetY()
+{
+    if (READER_PAGES.dataset.globalZoomOffset !== undefined)
+    {
+        return parseFloat(READER_PAGES.dataset.globalZoomOffset.split(',')[1]);
     }
 
-    return 0.0
+    return 0.0;
 }
 
-function loadZoomsFromImgTagsIfRequired(){
-    
+function loadZoomsFromImgTagsIfRequired()
+{
     // Zooms may be defined by another JS file
-    if (PAGES_ZOOMS == null){
-        
-        PAGES_ZOOMS = []
+    if (PAGES_ZOOMS === null)
+    {
+        PAGES_ZOOMS = [];
 
         // parse the data-zooms of each img and and the page number info
-        for (var i = 0; i < READER_PAGES.children.length; i++) {
-            
-            zooms_raw_data = READER_PAGES.children[i].dataset.zooms
+        for (let idx = 0; idx < READER_PAGES.children.length; idx += 1)
+        {
+            const zoomsRawData = READER_PAGES.children[idx].dataset.zooms;
 
             // ';' separates zooms data, ',' separates values
             // We add the page number (adding 1 because of indexing)
-            zooms = zooms_raw_data.split(";").map(
-                zoom => [i + 1].concat(
+            const zooms = zoomsRawData.split(";").map(
+                zoom => [idx + 1].concat(
                     zoom.split(',').map(
                         value => parseFloat(value)
                     )
                 )
-            )
+            );
 
-            PAGES_ZOOMS = PAGES_ZOOMS.concat(zooms)
-        }
-        
-    }
-    
-}
-
-function getFirstZoomOfPage(pageNumber){
-   
-    for (var zoom_idx = 0; zoom_idx < PAGES_ZOOMS.length; zoom_idx++){
-        if (PAGES_ZOOMS[zoom_idx][0] == pageNumber) {
-            return zoom_idx
+            PAGES_ZOOMS = PAGES_ZOOMS.concat(zooms);
         }
     }
 }
 
-function getLastZoomOfPage(pageNumber){
-    let res = null
+function getFirstZoomOfPage(pageNumber)
+{
+    for (let zoomIdx = 0; zoomIdx < PAGES_ZOOMS.length; zoomIdx += 1)
+    {
+        if (PAGES_ZOOMS[zoomIdx][0] === pageNumber)
+        {
+            return zoomIdx;
+        }
+    }
+}
 
-    for (var zoom_idx = 0; zoom_idx < PAGES_ZOOMS.length; zoom_idx++){
-        if (PAGES_ZOOMS[zoom_idx][0] == pageNumber) {
-            res = zoom_idx
+function getLastZoomOfPage(pageNumber)
+{
+    let res = null;
+
+    for (let zoomIdx = 0; zoomIdx < PAGES_ZOOMS.length; zoomIdx += 1)
+    {
+        if (PAGES_ZOOMS[zoomIdx][0] === pageNumber)
+        {
+            res = zoomIdx;
         }
 
-        if (res != null && PAGES_ZOOMS[zoom_idx][0] != pageNumber) {
-            break
+        if (res !== null && PAGES_ZOOMS[zoomIdx][0] !== pageNumber)
+        {
+            break;
         }
     }
 
-    return res
+    return res;
 }
 
-function getZoomCountForPage(pageNumber) {
-    return PAGES_ZOOMS.filter(zoom => zoom[0] == pageNumber).length
+function getZoomCountForPage(pageNumber)
+{
+    return PAGES_ZOOMS.filter(zoom => zoom[0] === pageNumber).length;
 }
 
-function getCurrentZoomIndexForPage() {
-    previousZoomsCount = PAGES_ZOOMS.filter(zoom => zoom[0] < CURRENT_PAGE).length
-    return CURRENT_ZOOM - previousZoomsCount + 1
+function getCurrentZoomIndexForPage()
+{
+    const previousZoomsCount = PAGES_ZOOMS.filter(zoom => zoom[0] < CURRENT_PAGE).length;
+    return CURRENT_ZOOM - previousZoomsCount + 1;
 }
 
-function getReadingProgressPercent() {
-    progressPerPage = 1 / getPagesCount()
+function getReadingProgressPercent()
+{
+    const progressPerPage = 1 / getPagesCount();
 
-    if (IS_PAGE_MODE){
-        return 100 * progressPerPage * CURRENT_PAGE
+    if (IS_PAGE_MODE)
+    {
+        return 100 * progressPerPage * CURRENT_PAGE;
     }
 
-    progressPerZoom = progressPerPage / getZoomCountForPage(CURRENT_PAGE)
+    const progressPerZoom = progressPerPage / getZoomCountForPage(CURRENT_PAGE);
 
-    readingProgress = (CURRENT_PAGE - 1) * progressPerPage + getCurrentZoomIndexForPage() * progressPerZoom
+    const readingProgress = (CURRENT_PAGE - 1) * progressPerPage + getCurrentZoomIndexForPage() * progressPerZoom;
 
-    return 100 * readingProgress
+    return 100 * readingProgress;
 }
 
-function updateProgressBar(){
-    PROGRESS_BAR.style.width = getReadingProgressPercent() + "%"
+function updateProgressBar()
+{
+    PROGRESS_BAR.style.width = getReadingProgressPercent() + "%";
 }
 
 // Dimensions utilites
 // -------------------
 
-function getPagesCount() {
-    return READER_PAGES.childElementCount
+function getPagesCount()
+{
+    return READER_PAGES.childElementCount;
 }
 
-function pageOriginalHeight(pageNumber) {
-    return READER_PAGES.children[pageNumber - 1].naturalHeight
+function pageOriginalHeight(pageNumber)
+{
+    return READER_PAGES.children[pageNumber - 1].naturalHeight;
 }
 
-function pageOriginalWidth(pageNumber) {
-    return READER_PAGES.children[pageNumber - 1].naturalWidth
+function pageOriginalWidth(pageNumber)
+{
+    return READER_PAGES.children[pageNumber - 1].naturalWidth;
 }
 
-function readerFrameRatio() {
-    return READER_CONTENT_FRAME.clientWidth / READER_CONTENT_FRAME.clientHeight
+function readerFrameRatio()
+{
+    return READER_CONTENT_FRAME.clientWidth / READER_CONTENT_FRAME.clientHeight;
 }
 
-function pageRatio(pageNumber) {
-    return READER_PAGES.children[pageNumber - 1].naturalWidth / READER_PAGES.children[pageNumber - 1].naturalHeight
+function pageRatio(pageNumber)
+{
+    return READER_PAGES.children[pageNumber - 1].naturalWidth / READER_PAGES.children[pageNumber - 1].naturalHeight;
 }
 
-function pageMaxHeight(){
-    let max_height = 0
+function pageMaxHeight()
+{
+    let maxHeight = 0;
 
-    for (var i = 0; i < READER_PAGES.children.length; i++) {
-        if(READER_PAGES.children[i].naturalHeight > max_height){
-            max_height = READER_PAGES.children[i].naturalHeight
+    for (let i = 0; i < READER_PAGES.children.length; i += 1)
+    {
+        if(READER_PAGES.children[i].naturalHeight > maxHeight)
+        {
+            maxHeight = READER_PAGES.children[i].naturalHeight;
         }
     }
 
-    return max_height
+    return maxHeight;
 }
 
-function pageVerticalOffset(pageNumber) {
-    return ( pageMaxHeight() - pageOriginalHeight(pageNumber) ) / 2
+function pageVerticalOffset(pageNumber)
+{
+    return ( pageMaxHeight() - pageOriginalHeight(pageNumber) ) / 2;
 }
 
-function previousPagesWidth(pageNumber) {
+function previousPagesWidth(pageNumber)
+{
     // The width of all previous pages relative to the provided index
 
-    let totalWidth = 0
+    let totalWidth = 0;
 
-    for (let idx = 0; idx < pageNumber - 1; idx++){
-        totalWidth = totalWidth + READER_PAGES.children[idx].naturalWidth
+    for (let idx = 0; idx < pageNumber - 1; idx += 1)
+    {
+        totalWidth += READER_PAGES.children[idx].naturalWidth;
     }
 
-    return totalWidth
+    return totalWidth;
 }
 
 // =========
 //  ACTIONS
 // =========
 
-function initReader(){
-    loadZoomsFromImgTagsIfRequired()
-    moveReaderDisplayToZoom(0)
+function initReader()
+{
+    VERSION_DISPLAY.innerText = VERSION_DISPLAY.innerText.replace("Unknown version", MELPOMENE_VERSION);
+    
+    loadZoomsFromImgTagsIfRequired();
+    moveReaderDisplayToZoom(0);
 
     // Smoothly show pictures when they intersect with the viewport
-    let visibilityObserver = new IntersectionObserver((entries, observer) => {
-        entries.forEach((entry) => {
-            if (entry.isIntersecting) {
-                entry.target.style.opacity = 1
-                entry.target.style.visibility = "visible"
-            } else {
-                entry.target.style.opacity = 0
-                entry.target.style.visibility = "hidden"
+    const visibilityObserver = new IntersectionObserver(
+        (entries, observer) =>
+        {
+            entries.forEach((entry) =>
+            {
+                if (entry.isIntersecting)
+                {
+                    entry.target.style.opacity = 1;
+                    entry.target.style.visibility = "visible";
+                }
+                
+                else
+                {
+                    entry.target.style.opacity = 0;
+                    entry.target.style.visibility = "hidden";
                 }
             });
-    }, { root: READER_CONTENT_FRAME, rootMargin: "-10px" });
+        },
+        { root: READER_CONTENT_FRAME, rootMargin: "-10px" }
+    );
 
-    for (var i = 0; i < READER_PAGES.children.length; i++) {
-        let img = READER_PAGES.children[i];
-        visibilityObserver.observe(img)
+    for (let i = 0; i < READER_PAGES.children.length; i += 1)
+    {
+        const img = READER_PAGES.children[i];
+        visibilityObserver.observe(img);
 
-        PROGRESS_BAR_PAGES.appendChild(document.createElement("div"))
+        PROGRESS_BAR_PAGES.appendChild(document.createElement("div"));
     }
 
-    READER_PAGES.style.display = "flex"
+    READER_PAGES.style.display = "flex";
 
-    setTimeout(() => {
-        READER_PAGES.hidden = false
-    }, "300")
+    setTimeout(
+        () => { READER_PAGES.hidden = false },
+        "300"
+    );
 
-    setTimeout(() => {
+    setTimeout(
+        () =>
+        {
             HELP_CONTROLS.style.opacity = null;
             HELP_CONTROLS.style.transform = null;
-    }, DELAY_BEFORE_HIDDING_CONTROLS)
+        },
+        DELAY_BEFORE_HIDDING_CONTROLS
+    );
 }
 
 
-function moveReaderDisplayToArea(pageNumber, width, height, posx, posy){
-    
+function moveReaderDisplayToArea(pageNumber, oWidth, oHeight, oPosx, oPosy)
+{
     // Keep original values for registering
-    o_width = width
-    o_height = height
-    o_posx = posx
-    o_posy = posy
+    let width = oWidth;
+    let height = oHeight;
+    let posx = oPosx;
+    let posy = oPosy;
 
     // Apply global offsets before scales if we are displaying a zoom
     // Pages display uses width & height = 0
-    if (width != 0 || height != 0){
-        width = width * globalZoomScale()
-        height = height * globalZoomScale()
-        posx = (posx + globalZoomOffsetX()) * globalZoomScale()
-        posy = (posy + globalZoomOffsetY()) * globalZoomScale()
+    if (width !== 0 || height !== 0)
+    {
+        width = width * globalZoomScale();
+        height = height * globalZoomScale();
+        posx = (posx + globalZoomOffsetX()) * globalZoomScale();
+        posy = (posy + globalZoomOffsetY()) * globalZoomScale();
     }
 
     // reduce width if offset sent us outside of page
-    if (posx < 0) {
-        width = width + posx
-        posx = 0
+    if (posx < 0)
+    {
+        width = width + posx;
+        posx = 0;
     }
-    if ((posx + width) > pageOriginalWidth(pageNumber)) {
-        width = pageOriginalWidth(pageNumber) - posx
+    
+    if ((posx + width) > pageOriginalWidth(pageNumber))
+    {
+        width = pageOriginalWidth(pageNumber) - posx;
     }
 
     // reduce height if offset sent us outside of page
-    if (posy < 0) {
-        height = height + posy
-        posy = 0
+    if (posy < 0)
+    {
+        height = height + posy;
+        posy = 0;
     }
-    if ((posy + height) > pageOriginalHeight(pageNumber)) {
-        height = pageOriginalHeight(pageNumber) - posy
+    
+    if ((posy + height) > pageOriginalHeight(pageNumber))
+    {
+        height = pageOriginalHeight(pageNumber) - posy;
     }
 
 
     // Align the top-left corner of the frame with the page
-    READER_PAGES.style.transform = "translate(-" + previousPagesWidth(pageNumber) + "px, -" + pageVerticalOffset(pageNumber) + "px )"
+    READER_PAGES.style.transform = "translate(-" + previousPagesWidth(pageNumber) + "px, -" + pageVerticalOffset(pageNumber) + "px )";
 
     // Then move so the top-left point of the zoom match the frame top-left
-    READER_PAGES.style.transform = "translate(" + (- posx) + "px, " + (-posy) + "px )" + READER_PAGES.style.transform
+    READER_PAGES.style.transform = "translate(" + (- posx) + "px, " + (-posy) + "px )" + READER_PAGES.style.transform;
 
     // Then, scale so the zoom would fit the frame, and center the zoom
-    if (width == 0){
-        width = pageOriginalWidth(pageNumber)
+    if (width === 0)
+    {
+        width = pageOriginalWidth(pageNumber);
     }
 
-    if (height == 0){
-        height = pageOriginalHeight(pageNumber)
+    if (height === 0)
+    {
+        height = pageOriginalHeight(pageNumber);
     }
 
-    zoomRatio = width / height
+    const zoomRatio = width / height;
 
-    if (readerFrameRatio() > zoomRatio) {
+    if (readerFrameRatio() > zoomRatio)
+    {
         // Frame wider than zoom => scale so heights are the same, offset on x
-        var zoomToFrameScaleFactor = READER_CONTENT_FRAME.clientHeight / height
+        const zoomToFrameScaleFactor = READER_CONTENT_FRAME.clientHeight / height;
 
-        READER_PAGES.style.transform = "scale(" + zoomToFrameScaleFactor + ")" + READER_PAGES.style.transform
+        READER_PAGES.style.transform = "scale(" + zoomToFrameScaleFactor + ")" + READER_PAGES.style.transform;
 
-        var scaledWidth = width * zoomToFrameScaleFactor
-        var offset = (READER_CONTENT_FRAME.clientWidth - scaledWidth) / 2
+        const scaledWidth = width * zoomToFrameScaleFactor;
+        const offset = (READER_CONTENT_FRAME.clientWidth - scaledWidth) / 2;
 
-        READER_PAGES.style.transform = "translateX(" + offset + "px)" + READER_PAGES.style.transform
+        READER_PAGES.style.transform = "translateX(" + offset + "px)" + READER_PAGES.style.transform;
 
-        updateFocusByWidth(scaledWidth)
-    } else {
+        updateFocusByWidth(scaledWidth);
+    }
+    
+    else
+    {
         // Frame narower than zoom => scale so left/right match, offset on y
-        var zoomToFrameScaleFactor = READER_CONTENT_FRAME.clientWidth / width 
+        const zoomToFrameScaleFactor = READER_CONTENT_FRAME.clientWidth / width;
 
-        READER_PAGES.style.transform = "scale(" + zoomToFrameScaleFactor + ")" + READER_PAGES.style.transform
+        READER_PAGES.style.transform = "scale(" + zoomToFrameScaleFactor + ")" + READER_PAGES.style.transform;
 
-        var scaledHeight = height * zoomToFrameScaleFactor
-        var offset = (READER_CONTENT_FRAME.clientHeight - scaledHeight) / 2
+        const scaledHeight = height * zoomToFrameScaleFactor;
+        const offset = (READER_CONTENT_FRAME.clientHeight - scaledHeight) / 2;
 
-        READER_PAGES.style.transform = "translateY(" + offset + "px)" + READER_PAGES.style.transform
+        READER_PAGES.style.transform = "translateY(" + offset + "px)" + READER_PAGES.style.transform;
 
-        updateFocusByHeight(scaledHeight)
+        updateFocusByHeight(scaledHeight);
     }
 
     // Use values before global offset / scale
-    CURRENT_PAGE = pageNumber
-    CURRENT_WIDTH = o_width
-    CURRENT_HEIGHT = o_height
-    CURRENT_X = o_posx
-    CURRENT_Y = o_posy
+    CURRENT_PAGE = pageNumber;
+    CURRENT_WIDTH = oWidth;
+    CURRENT_HEIGHT = oHeight;
+    CURRENT_X = oPosx;
+    CURRENT_Y = oPosy;
 }
 
-function refreshReaderDisplay() {
-    moveReaderDisplayToArea(CURRENT_PAGE, CURRENT_WIDTH, CURRENT_HEIGHT, CURRENT_X, CURRENT_Y)
+function refreshReaderDisplay()
+{
+    moveReaderDisplayToArea(CURRENT_PAGE, CURRENT_WIDTH, CURRENT_HEIGHT, CURRENT_X, CURRENT_Y);
 }
 
-function moveReaderDisplayToPage(pageNumber) {
-    moveReaderDisplayToArea(pageNumber, 0, 0, 0, 0)
+function moveReaderDisplayToPage(pageNumber)
+{
+    moveReaderDisplayToArea(pageNumber, 0, 0, 0, 0);
 }
 
-function moveReaderDisplayToZoom(index) {
+function moveReaderDisplayToZoom(index)
+{
+    moveReaderDisplayToArea(PAGES_ZOOMS[index][0], PAGES_ZOOMS[index][1], PAGES_ZOOMS[index][2], PAGES_ZOOMS[index][3], PAGES_ZOOMS[index][4]);
 
-    moveReaderDisplayToArea(PAGES_ZOOMS[index][0], PAGES_ZOOMS[index][1], PAGES_ZOOMS[index][2], PAGES_ZOOMS[index][3], PAGES_ZOOMS[index][4])
-    
-    CURRENT_ZOOM = index
+    CURRENT_ZOOM = index;
 }
 
-function updateFocusByWidth(width){
-    FOCUS_OVERLAY_WIDTH.style.width = (width / READER_CONTENT_FRAME.clientWidth * 100) + "%"
-    FOCUS_OVERLAY_HEIGHT.style.height = "100%"
+function updateFocusByWidth(width)
+{
+    FOCUS_OVERLAY_WIDTH.style.width = (width / READER_CONTENT_FRAME.clientWidth * 100) + "%";
+    FOCUS_OVERLAY_HEIGHT.style.height = "100%";
 }
 
-function updateFocusByHeight(height){
-    FOCUS_OVERLAY_WIDTH.style.width = "100%"
-    FOCUS_OVERLAY_HEIGHT.style.height = (height / READER_CONTENT_FRAME.clientHeight * 100) + "%"
+function updateFocusByHeight(height)
+{
+    FOCUS_OVERLAY_WIDTH.style.width = "100%";
+    FOCUS_OVERLAY_HEIGHT.style.height = (height / READER_CONTENT_FRAME.clientHeight * 100) + "%";
 }
 
-function toggleViewMode() {
-    if (IS_PAGE_MODE){
-        if (CURRENT_ZOOM != null){
-            moveReaderDisplayToZoom(CURRENT_ZOOM)
-        } else {
-            moveReaderDisplayToZoom(getFirstZoomOfPage(CURRENT_PAGE))
-        }
-        IS_PAGE_MODE = false
-    } else {
-        moveReaderDisplayToPage(CURRENT_PAGE)
-        IS_PAGE_MODE = true
+function toggleViewMode()
+{
+    if (IS_PAGE_MODE)
+    {
+        if (CURRENT_ZOOM !== null)
+        {
+            moveReaderDisplayToZoom(CURRENT_ZOOM);
         }
         
-    updateProgressBar()
+        else
+        {
+            moveReaderDisplayToZoom(getFirstZoomOfPage(CURRENT_PAGE));
+        }
+        
+        IS_PAGE_MODE = false;
+    }
+    
+    else
+    {
+        moveReaderDisplayToPage(CURRENT_PAGE);
+        IS_PAGE_MODE = true;
+    }
+
+    updateProgressBar();
 }
 
-function moveReader(to_next) {
-        
-    if (IS_PAGE_MODE){
-        if (to_next && CURRENT_PAGE < getPagesCount()) {
-            moveReaderDisplayToPage(CURRENT_PAGE + 1)
-            CURRENT_ZOOM = null
+function moveReader(toNext)
+{
+    if (IS_PAGE_MODE)
+    {
+        if (toNext && CURRENT_PAGE < getPagesCount())
+        {
+            moveReaderDisplayToPage(CURRENT_PAGE + 1);
+            CURRENT_ZOOM = null;
         }
 
-        else if (!to_next && CURRENT_PAGE > 1) {
-            moveReaderDisplayToPage(CURRENT_PAGE - 1)
-            CURRENT_ZOOM = null
-        }
-    
-    } else {
-    
-        if (to_next && CURRENT_ZOOM < PAGES_ZOOMS.length - 1) {
-            moveReaderDisplayToZoom(CURRENT_ZOOM + 1)
-        }
-        
-        else if (!to_next && CURRENT_ZOOM > 0) {
-            moveReaderDisplayToZoom(CURRENT_ZOOM - 1)
+        else if (!toNext && CURRENT_PAGE > 1)
+        {
+            moveReaderDisplayToPage(CURRENT_PAGE - 1);
+            CURRENT_ZOOM = null;
         }
     }
     
-    updateProgressBar()
+    else
+    {
+        if (toNext && CURRENT_ZOOM < PAGES_ZOOMS.length - 1)
+        {
+            moveReaderDisplayToZoom(CURRENT_ZOOM + 1);
+        }
 
+        else if (!toNext && CURRENT_ZOOM > 0)
+        {
+            moveReaderDisplayToZoom(CURRENT_ZOOM - 1);
+        }
+    }
+
+    updateProgressBar();
 }
 
 
@@ -425,69 +501,89 @@ function moveReader(to_next) {
 //   CALLBACKS
 // =============
 
-function handleKeyPress(key){
-    
-    if (key == MOVE_NEXT) {
-        moveReader(true)
+function handleKeyPress(key)
+{
+    if (key === MOVE_NEXT)
+    {
+        moveReader(true);
     }
 
-    else if (key == MOVE_BACK) {
-        moveReader(false)
+    else if (key === MOVE_BACK)
+    {
+        moveReader(false);
     }
 
-    else if (key.toUpperCase() == TOGGLE_FULLSCREEN){
-        if (document.fullscreenElement == null){
+    else if (key.toUpperCase() === TOGGLE_FULLSCREEN)
+    {
+        if (document.fullscreenElement === null)
+        {
             READER_FRAME.requestFullscreen();
-        } else {
+        }
+        
+        else
+        {
             document.exitFullscreen();
         }
-        
     }
 
-    else if (key.toUpperCase() == TOGGLE_PROGRESSBAR){
-        if (PROGRESS_BAR_CONTAINER.hidden == true) {
-            PROGRESS_BAR_CONTAINER.hidden = false
-        } else {
-            PROGRESS_BAR_CONTAINER.hidden = true
+    else if (key.toUpperCase() === TOGGLE_PROGRESSBAR)
+    {
+        if (PROGRESS_BAR_CONTAINER.hidden === true)
+        {
+            PROGRESS_BAR_CONTAINER.hidden = false;
         }
+        
+        else
+        {
+            PROGRESS_BAR_CONTAINER.hidden = true;
+        }
+        
         refreshReaderDisplay();
     }
 
-    else if (key.toUpperCase() == TOGGLE_VIEW_MODE) {
-        toggleViewMode()
+    else if (key.toUpperCase() === TOGGLE_VIEW_MODE)
+    {
+        toggleViewMode();
     }
-
 }
 
-function handleMouseWhell(event){
-    
+function handleMouseWhell(event)
+{
     // Only handle scroll event if the target is the nav controls
     // to avoid preventing page scrolling.
 
     // Do disable page scrolling when we do prev/next, though
 
-    if (! READER_FRAME.contains(event.target)){
-        return
+    if (! READER_FRAME.contains(event.target))
+    {
+        return;
     }
 
-    event.preventDefault()
-    event.stopPropagation()
+    event.preventDefault();
+    event.stopPropagation();
 
-    if (MOUSEWHELL_WAIT){
-        return
-    } else {
-        MOUSEWHELL_WAIT = true
-        setTimeout(() => {
-            MOUSEWHELL_WAIT = false
-        }, MOUSEWHELL_MIN_DELAY)
+    if (MOUSEWHELL_WAIT)
+    {
+        return;
     }
     
-    if (event.deltaY > 0) {
-        moveReader(true, false)
+    else
+    {
+        MOUSEWHELL_WAIT = true;
+        setTimeout(
+            () => { MOUSEWHELL_WAIT = false; },
+            MOUSEWHELL_MIN_DELAY
+        );
     }
 
-    else {
-        moveReader(false, false)
+    if (event.deltaY > 0)
+    {
+        moveReader(true, false);
+    }
+
+    else
+    {
+        moveReader(false, false);
     }
 }
 
@@ -495,19 +591,26 @@ function handleMouseWhell(event){
 //  INIT
 // ======
 
-window.addEventListener("load", (event) => {
-  VERSION_DISPLAY.innerText = VERSION_DISPLAY.innerText.replace("Unknown version", MELPOMENE_VERSION)
-  initReader()
-});
+window.addEventListener(
+    "load",
+    (event) => { initReader() }
+);
 
-addEventListener("resize", (event) => {
-    refreshReaderDisplay();
-});
+addEventListener(
+    "resize",
+    (event) => { refreshReaderDisplay() }
+);
 
-addEventListener("keydown", (event) => {
+addEventListener(
+    "keydown",
+    (event) =>
+    {
         handleKeyPress(event.key, event.shiftKey)
-});
+    }
+);
 
-addEventListener("wheel", (event) => {
-    handleMouseWhell(event)
-}, { passive:false });
+addEventListener(
+    "wheel",
+    (event) => { handleMouseWhell(event) },
+    { passive:false }
+);