I am not able to call a function in Javascript from browser [duplicate]

Code Snippet

When I click on Write button nothing is happening. Also it is showing an error ‘Cannot read properties of null (reading ‘addEventListener’)’ in browser console.

I was expecting that after I click on ‘Write’ button on browser, the function in Javascript file will be called. First it will show a prompt with “Inside Function” after that it will print “Hello All” on console.