javascript what is 'global object'? code example

Example: global object in javascript

var x = {name: "John"};	// This is a global object
for(let i=0; i<10; i++){
  	// Variable x is alive here
	// Variable i is alive here
  	
  	let a = 3;
  	// Variable a is alive here
  	
  	var y = 0;
  	// Variable y is alive here
}
// Variable i is dead here
// Variable a is dead here
// Variable x is alive here
// Variable y is alive here
console.log(x);	// {name: "John"}
console.log(y); // 0