CodePen

HTML

            
              <p>
  A bunch of content that actually exists in the DOM is here.
</p>
            
          
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CSS

            
              /* Just for readability */
p{
  padding:1em;
  border:2px solid red;
}

/* Now the example: */
p::after{
  content:"THIS sentence is generated via ::after."
}
            
          
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JS

            
              
            
          
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