added comments for improved readability

public/index.js

+// Object which stores all the user selected/entered values
 let inputObj = {
-    textChoice: 'manual',
-    text: '',
-    textLength: '',
-    readerLevel: '',
-    readerCategory: ''
+    textChoice: 'manual',   // choice of text entry initially set as manual. Can have values manual, calculated
+    text: '',               // User entered text in case of manual  
+    textLength: '',         // number of characters in text. Either from user enetered text or user entered number
+    readerLevel: '',        // Value of reader level selected from dropdown
+    readerCategory: ''      // Value of reader category selected from dropdown
 };
 
+
+// function handleTextRadioClick: responsible for showing or hiding text input / text length input based on selected option
 function handleTextRadioClick() {
     let textChoice = document.querySelector('input[name="text-input-option"]:checked').value;
-    console.log(textChoice);
     inputObj.textChoice = textChoice;
     toggleElement('character-calculation-wrapper');
     toggleElement('manual-character-input');
 }
 
+
+// function toggleElement: hides/shows the html element based on current visibility. 
+// accepts value of id attribute of element as parameter
 function toggleElement(id) {
-    let x = document.getElementById(id);
-    if (x.style.display === "none") {
-        x.style.display = "block";
+    let element = document.getElementById(id);
+    if (element.style.display === "none") {
+        element.style.display = "block";
     } else {
-        x.style.display = "none";
+        element.style.display = "none";
     }
 }
 
+
+// function handleTextAreaChange: captures the changes as user enters the text and gets the length
+// and sets number of characters to property textLength on inputObj
 function handleTextAreaChange() {
     let value = document.getElementById("manual-text-entry").value;
     value = value.trim();
@@ -32,23 +40,23 @@ function handleTextAreaChange() {
     document.getElementById("calculatedTextCharacters").setAttribute('value', characters)
 }
 
+
+// function handleCharacterInputChange: captures changes in number of characters input field
+// and sets number of characters to property textLength on inputObj
 function handleCharacterInputChange() {
     let value = document.getElementById("inputTextCharacters").value;
     setCharacterLength(value);
 }
 
+// function setCharacterLength: sets number of characters to property textLength on inputObj
 function setCharacterLength(characters) {
-    inputObj.textLength = characters;
-    console.log('Character length: ' + inputObj.textLength);
+    inputObj.textLength = parseInt(characters);
 }
 
-function calculateReadingTime() {
-    if (isFormValid()) {
-        let x = document.getElementById('calculate-time-element');
-        x.style.display = "block";
-    }
-}
 
+// function isFormValid: checks for mandatory input fields and validates te form 
+// returns true if all values are filled else returns false
+// also shows error messages for respective inputs fields
 function isFormValid() {
     let invalidFields = 0;
     if (inputObj.textChoice === 'manual' && inputObj.text === '') {
@@ -80,20 +88,47 @@ function isFormValid() {
     }
 
     return invalidFields < 1
-
 }
 
+
+// function showFeedbackForm: displays feedback form when calculation is done
 function showFeedbackForm() {
-    let x = document.getElementById('feedback-form');
-    x.style.display = "block";
+    let element = document.getElementById('feedback-form');
+    element.style.display = "block";
 }
 
+
+// function readerLevelChangeEvent: listens for change in reader level dropdown
+// and sets selected value to property readerLevel on inputObj
 function readerLevelChangeEvent(event) {
-    console.log(event.target.value)
     inputObj.readerLevel = event.target.value;
 }
 
+// function readerCategoryChangeEvent: listens for change in reader category dropdown
+// and sets selected value to property readerCategory on inputObj
 function readerCategoryChangeEvent(event) {
-    console.log(event.target.value)
     inputObj.readerCategory = event.target.value;
 }
+
+
+// function calculateReadingTime: This function is responsible for calculating reading time
+// reading time can be calculated if all inputs are valid
+function calculateReadingTime() {
+
+    if (isFormValid()) {
+
+        //variable x which holds final reading time in minutes
+        let x = 0;
+
+        console.log(inputObj);
+
+        // TODO: logic or algorithm for calulating reading time goes here
+            // inputObj.textLength has number of characters (number data type)
+            // inputObj.readerLevel has level of reader (string data type)
+            // inputObj.readerCategory has category of reader (string data type)
+
+        // display html element which shows time
+        let element = document.getElementById('calculate-time-element');
+        element.style.display = "block";
+    }
+}