javascript - Problems with addEventListener in js

Question

After adding addEventListener to another element
Screenshot 2017-06-15 21.07.43

Result error
Screen snapshot 2017-06-15 21.02.27

I’m confused, I don’t know where I wrote it wrong.
Please give me a solution. . .

Answer 1

Readdata is definitely an element? You can use console.log(readdata) to see the type and it will be clear