How to disable duplicate input?

Question

JavaScript

update.
https://jsfiddle.net/1yhxwof9/----------------------------------------

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and take into account that each next word - starts with the letter
that the previous one ends with
https://jsfiddle.net/a3yv0971/1/

Answer 1

Check if the new value is already in cities , compare the first letter of the new value and the last letter of the last value in cities .