Znajdź nie jest funkcją JavaScript

This may occur if the variable or value 
which .find() is called is not an array

To solve the error, 
1. make sure the variable or value is an array, if not
2. convert the value to an array before calling the .find() method

To convert to an array, use Array.from(value),


ADVANCED
To convert a nodelist to an array, visit this link
https://www.codegrepper.com/search.php?q=convert%20elements%20to%20array%20javascript
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