main.js

/**
 * Get the editable instance.
 */
let editable = document.querySelector("[contenteditable=true]");

/**
 * When focus is removed, run the `formatText` function
 */
editable.addEventListener('blur', formatText);

/**
 * Format the innerText of the SpongeBob meme
 */
function formatText(event){
    
    /* Format the text
     * Split the text into an array, for each character in the array, if the index of the letter is odd,
     * return the letter uppercase, otherwise return it lowercase
     * then join the array with no delimiter returning it to a normal string
     */
    let memedText = this.innerText.split("")
        .map(function (letter, i) {
            return i % 2 ? letter.toUpperCase() : letter.toLowerCase()
        }).join("")
    
    // Replace the old text with new text
    this.innerText = memedText;
}