Expressions & operators in javascript

const a = 1 + true // 2
const b = 1 + false // 1
const c = true + true // 2
const d = false + false // 0

let a = 1; // 1
a+=6; // 7
a-=4; // 3

// זה כמו לכתוב --->
let a = 1;
a = a + 6;
a= a - 4;

let a = 'abc';
a+='def'; // abcdef

const a = 0 < 1 ? true : false; // true

const val1 = 10;
const val2 = 20;
const a = val1 != val2 ? 'NO' : 'YES'; // 'YES'

// אפשר גם לשרשר

const a = 5 != 5 ? 'OK' : 5 < 5 ? 'NO' : 5 > 5 ? 'NO!!!' : 'EQUAL'; // 'EQUAL'

// נסדר את השורה למעלה כדאי שיהיה יותר ברור
const a = 5 != 5 ? 'OK' :
5 < 5 ? 'NO' :
5 > 5 ? 'NO!!!' :
'EQUAL'; // 'EQUAL'

// זה בדיוק כמו שנכתוב
let a;
if(5 != 5){
a = 'OK'
} else if(5 < 5){
a = 'NO';
} else if(5 > 5){
a = 'NO!!!';
} else{
a = 'EQUAL';
}

const a = {
	color:'red',
	name:'jon'
}

delete a.name;
console.log(a); // {color:'red'}

delete a['color'];
console.log(a); // {}

const a = 2**3; // 8
const b = 2**-3; // 0.125
const c = (2**3)**3; // 512

// זה הרבה יותר ברור מאשר
const d = Math.pow( Math.pow( 2 , 3 ) , 3 ); // 512

// כמובן שגם כאן אפשר לעשות
let e = 4;
e **= 3; // 64

let a = 5;
const b = a++; // b=5 , a=6 
const c = ++a; // c=7 , a=7

const d=5;
const e=5;
console.log(d==e) // true
console.log(d!=e) // false

const f=8;
console.log(e<f) // true
console.log(e>f) // false
console.log("aa"<"ab") // true

console.log(d<=e) // true
console.log(d>=e) // true

console.log(d<=e && e<f) // true
console.log(d<=e && e>f) // false

console.log(d<=e || e>f) // true
console.log(!(d<=e && e>f)) // true

const a = {name:'abc',title:'def'}
a instanceof Object // true

const b = ['aaa','bbb']
b instanceof Array // true

const n = new Number(123)
n instanceof Number // true

const nb = 123
n instanceof Number // false

const s = new String('abc')
s instanceof String // true

const sb = 'abc'
sb instanceof String // false

const a = null
const b = a ?? 'OK' // b='OK'

const a = 'abc'
const b = a ?? 'OK' // b='abc'

const c = {color:'red'}
c.color ??='blue' // c='red'
c.title ??='car' // there is no title to c object, but now there is :) c.title = 'car'

const obj = {
  title:'my obj', 
  colorOptions:{
    optionA:'red',
    optionB:'blur'
  }
}
console.log(obj.title) // 'my obj'
console.log(obj.title.name) // ERROR
console.log(obj.title?.name) // undefined
console.log(obj.colorOptions?.optionA) // 'red'
console.log(obj.colorOptions?.optionA?.color) // undefined

console.log(4 % 2) // 0
console.log(-4 % 2) // -0
console.log(4 % 3) // 1
console.log(-4 % 3) // -1
console.log(20 % 5) // 0

const a = [1,2,3];
const b = [3,4,5];
const c = [a,...b];
console.log(c) // [[1,2,3],3,4,5]

const c = [...a,...b];
console.log(c) // [1,2,3,3,4,5]

const c = {...a};
console.log(c) // {0: 1, 1: 2, 2: 3}

const c = ['aaa',...a,'bbb']
console.log(c) // ['aaa', 1, 2, 3, 'bbb']

const d = [2023,0,14] // for [YEAR,MONTH,DAY]
const c = new Date(d) // ERROR
console.log(c) // Invalid Date
const c = new Date(...d)
console.log(c) // Sat Jan 14 2023 00:00:00 GMT+0200 (Israel Standard Time)

const c = [...a] // now c is new copy of a but only first layer

typeof 1 === "number";
typeof "1" === "string";
typeof "" === "string";
typeof "aaa" === "string";
typeof true === "boolean";
typeof false === "boolean";
typeof Symbol("foo") === "symbol";
typeof undefined === "undefined";
typeof myVar === "undefined";
typeof { title: 'my obj' } === "object";
typeof [1, 2, 3] === "object";
typeof new Date() === "object";
typeof null === "object";
typeof function () {} === "function";