console.log('my'+' cat'); // my cat
console.log('1'+ 2); // 12
console.log(`string literals: 1 + 2 = ${1 + 2}`); // string literals: 1 + 2 = 3
console.log('amanda\s \n\tbook')
// amanda's
// book
// \ : ' , \n : 세로줄바꿈, \t : tab
console.log( 1 + 1 ); // add // 2
console.log( 1 - 1 ); // substract // 0
console.log( 1 / 1 ); // divide // 1
console.log( 1 * 1 ); // multiply // 1
console.log( 5 % 2 ); // remainder // 1
console.log( 2 ** 3 ); // exponentiation // 8
let counter = 2;
const preIncrement = ++counter;
// counter = counter + 1;
// preIncrement = counter;
console.log(`preIncrement: ${preIncrement}, counter: ${counter}`);
// preIncrement: 3, counter: 3
const postIncrement = counter++;
// postIncrement = counter;
// counter = counter + 1;
console.log(`postIncrement: ${postIncrement}, counter: ${counter}`);
// preIncrement: 3, counter: 4
const preDecrement = --counter;
console.log(`preDecrement: ${preDecrement}, counter: ${counter}`);
// preDecrement: 3, counter: 3
const postDecrement = counter--;
console.log(`postDecrement: ${postDecrement}, counter: ${counter}`);
// preIncrement: 3, counter: 2
let x = 3;
let y = 6;
x += y; // x = x + y;
x -= y; // x = x - y;
x *= y; // x = x * y;
x /= y; // x = x / y;
console.log(10 < 6); // less than // false
console.log(10 <= 6); // less the or equal // false
console.log(10 > 6); // greater than // true
console.log(10 >= 6) // greater than or equal // true
const value1 = false;
const value2 = 4 < 2;
// || (or), finds the first truthy value
// 첫번째로 true를 찾으면 나머지 조건은 계산하지 않음
// 연산을 많이하는 함수를 호출하거나 expration 같은 것들은 제일 마지막 조건으로 둔다
console.log(`or: ${value1 || value2 || check()}`); // or: true
// && (and), finds the first falsy value
// 첫번째로 false를 찾으면 나머지 조건은 계산하지 않음
console.log(`and: ${value1 || value2 || check()}`); // and : false
function check() {
for (let i = 0; i < 10; i++) {
//wasting time
console.log('😍')
}
return true;
}
// often used to compress long if-statement
nullableObject && unllableObject.somthing
if (nullableObject != null) {
nullableObject.somthing;
}
// ! (not)
console.log(!value1); // true
const stringFive = '5';
const numberFive = 5;
// == loose equality, with type conversion
console.log(stringFive == numberFive); // true
console.log(stringFive != numberFive); // false
// === strict equality, no type conversion
console.log(stringFive === numberFive); // false
console.log(stringFive !== numberfive); // true
// object equality by reference
const ellie1 = { name: 'ellie' };
const ellie2 = { name: 'ellie' };
const ellie3 = ellie1;
console.log(ellie1 == ellie2); // false
console.log(ellie1 === ellie2); // false
console.log(ellie1 === ellie3); // true
// equality - puzzler
console.log(0 == false); // true
consoel.log(0 === false); // false
consoel.log('' == false); // true
consoel.log('' === false); // false
consoel.log(null == undefined); // true
consoel.log(null === undefined); // false
if, else if, else
const name = 'df';
if (name === 'amadna') {
console.log('Welcome, Amadna!');
} else if (name === 'coder') {
console.log('You are amazing coder');
} else {
console.log('unknown');
}
// unknown
condition ? value1 : value2;
console.log(name === 'amadna' ? 'yes' : 'no'); // no
use for multiple if checks
use for enum-like value check
use for multiple type checks in TS
const browser = 'IE';
switch (browser) {
case 'IE':
console.log('go away!');
break;
case 'Chrome':
case 'FireFox':
console.log('I love You');
break;
default:
console.log('same all!');
break;
}
// go away!
while loop, while the condition is truthy,
body code is executed.
let i = 3;
while (i > 0) {
console.log(`while: ${i}`);
i--;
}
// while: 3
// while: 2
// while: 1
do while loop, body code is excuted first,
then check the condition
let i = 3;
while (i > 0) {
console.log(`while: ${i}`);
i--;
}
do {
console.log(`do while: ${i}`);
i--;
} while (i > 0);
// while: 3
// while: 2
// while: 1
// do while: 0
for (i = 3; i > 0; i++) {
console.log(`for: ${i}`);
}
for (let i = 3; i > 0; i = i - 2) {
// inline variable declaration
console.log(`inline variable for: ${i}`);
}
// nested loops
for (let i = 0; i < 10; i++) {
for (let j = 0; j < 10; j++) {
console.log(`i: ${i}, j: ${j}`);
}
Q1. iterate from 0 to 10 and print only even numbers (use continue)
for (let i = 0; i < 11; i++) {
if (i % 2 !== 0) {
continue;
}
console.log(`Q1. ${i}`);
}
for (let i = 0; i < 11; i++) {
if (i % 2 === 0) {
console.log(`Q1. ${i}`);
}
}
Q2. iterate from 0 to 10 and print numbers until reaching 8 (use break)
for (let i = 0; i < 11; i++) {
if (i > 8) {
break;
}
console.log(`Q2. ${i}`);
}