Why is element of 'for-of' loop undefined?

I'm trying to filter the displaying of objects in an array based on what a user types into a search box (in this example, by the property 'prev.author'). I'm using a 'for-of' loop. If you check my code, you can see that I put in checks to make sure the individual variable, prev, is defined.

When I run the code, both checks show it is defined. The 'value' variable is set to whatever the user types in the box, & it works. However, when I try to style the individual variable (prev), I get the error message "Uncaught TypeError: Cannot set properties of undefined (reading 'style')". How could this element, prev, be undefined? It seems like I defined it when initializing the loop. Any help would be much appreciated, as I've already spent a few hours on it.

for (const prev of displayedPrevs) {
     console.log(prev);
     console.log(prev.author);
     console.log(typeof prev.author);
     
     // First check to see if prev is defined returns 'defined'
     if (typeof prev === 'undefined') {
          console.log('undefined');
     } else {
          console.log('defined')
     }

     if (prev.author.toLowerCase().trim().includes(value)) {
          // Second check to see if prev is defined returns 'defined'
          if (typeof prev === 'undefined') {
               console.log('undefined');
          } else {
               console.log('defined');
          }

          console.log('yes');
          prev.style.display = 'block'; // error: "Uncaught TypeError: Cannot read 
                                                   properties of undefined (reading 'style')"
     } else {
          console.log('no');
          prev.style.display = 'none'; // error: "Uncaught TypeError: Cannot read 
                                          properties of undefined (reading 'style')"
     }
}