x = "hello";
console.log(x[0]);
x[0]="j";
console.log(x);
y = typeof (1);
console.log(y);
var z;
console.log(typeof z);
a = null;
console.log(typeof a);
console.log(a+z);
b = Symbol(1);
c = Symbol(1);
console.log(b==c ? true:false);
var name = ["john", 1, true, null, undefined];
console.log(name, typeof name, name[3]);
x=[]; //array
x[1] = "john";
x[3] = ' mary ';
console.log(x);
person = {name : "john", age : 10, gender : "male"}; //object
field = ["name", "age", "gender"]
a = "name";
console.log(person[field[0]], person.name)
