operator.js

// 1. String concatenation
console.log("my" + " cat");
console.log("1" + 2);
console.log(`string literals: 1 + 2 = ${1 + 2}`);

// 2. Numeric operatiors
console.log(1 + 1); // add
console.log(1 - 1); // substract
console.log(1 / 1); // divide
console.log(1 * 1); // multiply
console.log(5 % 2); // remainder
console.log(2 ** 3); //exponentiaion

// 3. Increment and decrement operators
let counter = 2;
const preIncrement = ++counter;
// counter = counter + 1;
// preIncrement = counter;
console.log(`preIncrement: ${preIncrement}, counter:${counter}`);
const postIncrement = counter++;
// postIncrement = counter;
// counter = counter + 1;
console.log(`postIncrement: ${postIncrement}, counter:${counter}`);

// 4. Assignment operators
let x = 3;
let y = 6;
x += y; // x = x + y;
x -= y;
x *= y;
x /= y;

// 5. Comparison operators
console.log(10 < 6); // less than
console.log(10 <= 6); // less than or equal
console.log(10 > 6); // greater than
console.log(10 >= 6); // greater than or equal

// 6. Logical operators : ||(or), &&(and), !(not)
const value1 = false;
const value2 = 4 < 2;

// || (or), finds the first truthy value(true값 출력시 멈춤)
// expression이나 함수를 맨뒤에 호출하는게 효율적인 코드
console.log(`or:${value1 || value2 || check()}`);

// && (and), finds the first falsy value
console.log(`or:${value1 || value2 || check()}`);

function check() {
  for (let i = 0; i < 10; i++) {
    //wasting time
    console.log("❤");
  }
  return true;
}

// ! (not)
console.log(!value1);

// 7. Equality
const stringFive = "5";
const numberFive = 5;

// == loose equality, with type conversion
console.log(stringFive == numberFive);
console.log(stringFive != numberFive);
// === strict equality, no type conversion
console.log(stringFive === numberFive);
console.log(stringFive !== numberFive);

// object equality by reference
const och1 = { name: "och" };
const och2 = { name: "och" };
const och3 = och1;
console.log(och1 == och2);
console.log(och1 === och2);
console.log(och1 === och3);

// equality - puzzler
console.log(0 == false);
console.log(0 === false);
console.log("" == false);
console.log("" === false);
console.log(null == undefined);
console.log(null === undefined);

// 8. Conditional operator : if
const name = "och";
if (name == "och") {
  console.log("welcome, och");
} else if (name === "coder") {
  console.log("you are amazing, coder");
} else {
  console.log("unknwon");
}

// 9. Ternary operator : ?
// condition ? value1 : value2; (간단할 경우만 사용)
console.log(name === "och" ? "yes" : "no");

// 10. Switch statement
// 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("love you!");
    break;
  default:
    console.log("same all!");
    break;
}

// 11. Loops
// while loop, while the condition is truthy
// body code is executed.
let i = 3;
while (i > 0) {
  console.log(`while: ${i}`);
  i--;
}

// do while loop, body code is executed first,
// then check the condition (블럭먼저 실행)
do {
  console.log(`do while: ${i}`);
  i--;
} while (i > 0);

// for loop, for(begin; condition ;step)
for (i = 3; i > 0; i--) {
  console.log(`for: ${i}`);
}

for (let i = 3; i > 0; 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}`);
  }
}

// break, continue
// 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}`);
}

// 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}`);
}