Viewing: ko.javascript.info

(, ) . . , .

.
(string), (number), bigint, (boolean), (symbol), null, undefined .

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

john.sayHi(); //  !

john , sayHi .

, , HTML (HTML element) . .

, .

(creator) .

, .

" " . , String,Number,Boolean, Symbol . .

let str = "Hello";

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

? str.toUpperCase () .

. ( ) .

let n = 1.23456;

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

, .

Java new Number(1) new Boolean(false) " " .

, . .

alert( typeof 0 ); // "number"

alert( typeof new Number(0) ); // "object"!

, .

let zero = new Number(0);

if (zero) { //  zero ,   .
  alert( "  zero   !?!" );
}

, new String / Number / Boolean . new (, , ) . .

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

null undefined (null/undefined) . " " , . " " .

alert(null.test); // error

Summary

          let str = "Hello";

str.test = 5;

alert(str.test);

, (str) (test) ? ?

let str = "Hello";

str.test = 5; // (*)

alert(str.test);

(*) , .