Javascript Basic

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)