Data type and variable-- Difference between JavaScript and C#

Hello. I am facing a little problem…The data type used in JavaScript looks like the Data type in C# for me.
Though I’m still learning C#, I need to study JavaScript concurrently. Now I am completely confused about difference between C# and JavaScript.
Could you check if my understanding is correct, please?

data type
[JavaScript]—[C#]
string----------string
number--------double
boolean--------boolean
function--------method(actually not a data type in C#)
null------------ Nullable value types???
object----------dictionary???
array-----------array

variable
[JavaScript]—[C#]
const----------const
let-------------var???
var------------object???