added comments

src/background.js

@@ -1,8 +1,11 @@
+// Query a WaniKani API endpoint with the given token
 const query = (token, url) => 
     new Promise(async (resolve, reject) => { 
+        // Create header with the authorization token
         const requestHeaders = new Headers()
         requestHeaders.append("Authorization", "Bearer " + token)
 
+        // Construct request
         const endpoint = new Request(
             url, 
             { 
@@ -11,6 +14,8 @@ const query = (token, url) =>
             }
         )
 
+        // Fetch the response. If it returns HTTP 200, resolve the promise,
+        // otherwise reject it
         var result = await fetch(endpoint)
         if(!result.ok)
         {
@@ -21,6 +26,7 @@ const query = (token, url) =>
         return resolve(result.json())
     })
 
+// Update the local cache with new data
 const updateCache = async (token, oldLevel, newLevel) => {
     // If oldLevel is undefined, then a sync has never been performed (first time user)
     if(oldLevel === undefined)

src/content.js

@@ -1,15 +1,18 @@
+// Vocab Furigana CSS
 var vocabStyle = `
     .furikani-vocabulary {
         display: none;
     }
 `
 
+// Kanji Furigana CSS
 var kanjiStyle  = `
     .furikani-kanji {
         display: none;
     }
 `
 
+// Create stylesheet elements on the website for the classes
 var vocabStyleSheet = document.createElement("style")
 var kanjiStyleSheet = document.createElement("style")
 
@@ -23,6 +26,7 @@ chrome.storage.local.get(["vocabulary", "kanji", "validUserLevel", "enabled", "e
     if(!data.validUserLevel)
         return
 
+    // If global setting is enabled, set the stylesheets depending on the other settings
     if(data.enabled)
     {
         if(data.enabledVocab)
@@ -45,7 +49,7 @@ chrome.storage.local.get(["vocabulary", "kanji", "validUserLevel", "enabled", "e
         var ruby = document.createElement("ruby")
         ruby.innerHTML = rubyTags.item(tag).innerHTML
 
-        // Remove all tags (except for <rb>)
+        // Remove all tags (except for <rb>, <span>)
         while(ruby.lastElementChild)
         {
             if(ruby.lastElementChild.tagName.toLowerCase() === "rb" ||
@@ -58,7 +62,8 @@ chrome.storage.local.get(["vocabulary", "kanji", "validUserLevel", "enabled", "e
             ruby.removeChild(ruby.lastElementChild)
         }
 
-        // If the contents of the <ruby> tag are in the word list, remove the <rt> tag
+        // If the contents of the <ruby> tag are in the word list, tag the <rt> tag
+        // with the correct class
         var rtTag = rubyTags.item(tag).getElementsByTagName("rt").item(0)
         if(vocabulary.includes(ruby.innerText))
             rtTag.classList.add("furikani-vocabulary")
@@ -68,11 +73,14 @@ chrome.storage.local.get(["vocabulary", "kanji", "validUserLevel", "enabled", "e
 })
 
 chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
+    // One of the switches was checked/unchecked
     if(msg.action === "settingsUpdated")
     {
+        // Retrieve current switch states
         chrome.storage.local.get(["enabled", "enabledVocab", "enabledKanji"], (data) => {  
             console.log(data)
-
+            
+            // If everything is disabled, disable all stylsheets
             if(!data.enabled)
             {
                 vocabStyleSheet.innerHTML = ""
@@ -81,6 +89,7 @@ chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 return
             }
 
+            // Otherwise set the kanji and vocab stylesheets depending on their settings
             vocabStyleSheet.innerHTML = data.enabledVocab ? vocabStyle : ""
             kanjiStyleSheet.innerHTML = data.enabledKanji ? kanjiStyle : ""
 

src/popup.js

@@ -9,21 +9,25 @@ const kanjiSetting = document.getElementById("setting-kanji")
 
 // Set popup content
 chrome.storage.local.get(["level", "token", "enabled", "enabledVocab", "enabledKanji"], (data) => {
+    // If no token is set, display exlamation mark and checkmark button
     if(data.token === undefined)
     {
         statusField.innerHTML = String.fromCodePoint(0x2757)
         submitButton.innerHTML = String.fromCodePoint(0x2705)
         submitButton.classList.add("no-token")
     }
-    else
+    else    // else display checkmark and reload button
     {
         statusField.innerHTML = String.fromCodePoint(0x2705)
         submitButton.innerHTML = String.fromCodePoint(0x1F501)
     }
 
+    // Display the users current WaniKani level
     const levelSpan = document.getElementById("level")
     levelSpan.innerHTML = data.level
 
+    // If the input field contains text that is not the current token, turn the
+    // button into a checkmark (else turn it into a repeat button)
     inputField.addEventListener("input", () => {
         if(inputField.value !== "" && inputField.value !== data.token)
         {
@@ -37,6 +41,7 @@ chrome.storage.local.get(["level", "token", "enabled", "enabledVocab", "enabledK
         }
     })
 
+    // Set the switches to thecached values
     globalSetting.checked = data.enabled
     vocabSetting.checked = data.enabledVocab
     kanjiSetting.checked = data.enabledKanji
@@ -74,6 +79,8 @@ submitButton.addEventListener( "click", () => {
 globalSetting.addEventListener("change", () => {
     chrome.storage.local.set({"enabled": globalSetting.checked})
 
+    // If the global settings are unchecked, uncheck the other options as well   
+    // and disable them
     if(!globalSetting.checked)
     {
         vocabSetting.checked = false
@@ -82,7 +89,8 @@ globalSetting.addEventListener("change", () => {
         vocabSetting.setAttribute("disabled", true)
         kanjiSetting.setAttribute("disabled", true)
     }
-    else
+    // Else restore the values of the switches and activate them agin
+    else   
     {
         chrome.storage.local.get(["enabledVocab", "enabledKanji"], (data) => {
             vocabSetting.checked = data.enabledVocab
@@ -93,6 +101,7 @@ globalSetting.addEventListener("change", () => {
         kanjiSetting.removeAttribute("disabled")
     }
 
+    // Send a message to content script that the switches were updated
     chrome.tabs.query({active: true, currentWindow: true}, (tabs) => {
         chrome.tabs.sendMessage(tabs[0].id, {action: "settingsUpdated"}, (r) => {})
     })