Variable scope in JavaScript , Hoisting, Execution context [duplicate]

I am a beginner for javascript, and I encountered something weird when I was trying to understand variable-scope. here is the code I wrote:

var year = 2020

function someFunction(){
    console.log(year) 
}
someFunction()

but then I redeclared the variable "year" again inside the function but after the console.log() statement like this :

var year = 2020

function someFunction(){
    
    console.log(year) 
    var year = 1999
}
someFunction()

and the output I got was: undefined

As a beginner, I found this hard to understand why . I hope you can help me. Thanks!