Why does node js think the variable is already declared?

Question

Node.js

Hello everyone, I'm new to node.js and faced this situation:
There are two files in the same folder and each of these files has a variable if the first file already has it, then the second file does not allow it to be declared because it thinks that it is already declared Cannot redeclare block-scoped variable 'a' . Can anyone explain why this behavior is happening?const a = 2
const a