자바스크립트 Boolean Logic

&& 모든것이 true이면 true를 반환. || 언제든 첫번째로 만나는 조건에 true이면 true를 반환. ! (NOT) true false 값을 반전시킴.

&& 예시

var firstName = "John";
var age = 20;

if(age < 13) {
  console.log(firstName + ' is a boy');
} else if (age >= 13 && age < 20) {
  console.log(firstName + ' is a teenager');
} else if (age >= 20 && age < 30) {
  console.log(firstName + ' is a young man');
} else {
  console.log(firstName + ' is a man');
}

**

** 예시

if(age < 13) {
  console.log(firstName + ' is a boy');
} else if (age >= 13 || age < 20) {
  console.log(firstName + ' is a teenager');
} else if (age >= 20 || age < 30) {
  console.log(firstName + ' is a young man');
} else {
  console.log(firstName + ' is a man');
}

! 예시

if(!age < 13) {
  console.log(firstName + ' is not a boy');
} else {
  console.log(firstName + ' is a boy');
}