what does !!var mean js code example

Example 1: variables in js

var Hello = "World";
let bool = false;
const int = 8788;

Example 2: js what does var mean

Used to create a variable that is globally scoped when not used in a function. 
When it is used in a function, it can only be used in that function and not
outside of it. This statement is comparable to let but more globalized.