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JavaScript ()()

11:

let john = {
  name: "John",
  sayHi: function() {
    alert("Hi buddy!");
  }
};

john.sayHi(); // Hi buddy!

sayHi john

HTML

JavaScript

JavaScript:

String, Number, Boolean, Symbol

let str = "Hello";

alert( str.toUpperCase() ); // HELLO

str.toUpperCase() :

JavaScript

let n = 1.23456;

alert( n.toFixed(2) ); // 1.23

Java new Number(1) new Boolean(false)

JavaScript

alert( typeof 1 ); // "number"

alert( typeof new Number(1) ); // "object"!

if true

let zero = new Number(0);

if (zero) { // zero  true, 
  alert( "zero is truthy?!?" );
}

new String/Number/Boolean : ()

let num = Number("123"); // string  number

null undefined

alert(null.test); // error

          let str = "Hello";

str.test = 5;

alert(str.test);

let str = "Hello";

str.test = 5; // (*)

alert(str.test);

2::

(*) :

str

(*)