fill_text.js

$input.addEventListener('keydown', e => {
    if(e.key === 'ArrowRight') {
        $span.textContent = ''; // clear ghost span 
        $input.textContent = rest + suggestion; // fill the $input bar with required suggestion
        
        // moves cursor to the end of the input box (won't go into the details of it)
        setEndOfContenteditable($input); 
    }
});