02_JavaScript: If & switch/case

02_JavaScript: If & switch/case

·

2 min read

Ex01. If

const a = 10;
if (a > 15) { //code block
    console.log('a is bigger than 15');
} else if ( a === 10) {
    console.log('a is 10');
} else {
    console.log('This is not a>15 and a===10');
}

Ex02. Switch/case

const device = 'iphone';
switch (device) {
    case 'iphone':
        console.log('This is iphone');
        break; //생략 가능 
    case 'ipad':
        console.log('This is ipad');
        break;
    default:
        console.log('sorry');
}

Ex03. Check if there is the certain value

function isAnimal(text) {
    return (
        text === 'cat' || text === 'dog' || text === 'turtle' || text === 'bear'
    );
}
console.log(isAnimal('dog')); // true
console.log(isAnimal('laptop')); // false

-> Change into the Array

function isAnimal(name) {
    const animals = ['cat', 'dog', 'turtle', 'bear'];
    return animals.includes(name);
}
console.log(isAnimal('dog')); //true
console.log(isAnimal('laptop')); //false

-> Change into the Arrow Function

const isAnimal = name => ['cat', 'dog', 'turtle', 'bear'].inclues(name);

console.log(isAnimal('dog')); //true
console.log(isAnimal('laptop')); //false

Ex04. Return the different values

(If ver.)

function getSound(animal) {
    if (animal === 'dog') return 'siru';
    if (animal === 'cat') return 'kitty';
    if (animal === 'bird') return 'huhu';
    return '...?';
}
console.log(getSound('dog')); //siru

(Switch ver.)

function getSound(animal) {
    switch(animal) {
        case 'dog':
            return 'siru';
        case 'cat':
            return 'kitty';
        case 'bird':
            return 'huhu';
        default:
            return '...?';
    }
}
console.log(getSound('dog')); //siru
  • Switch는 break 생략 가능

(Object ver.)

function getSound(animal) {
    const sounds = {
        dog: 'siru',
        cat: 'kitty',
        bird: 'huhu'
    };
    return sounds[animal] || '...?';
}
console.log(getSound('dog')); //siru
// 실행 해야하는 코드 구문이 다를 때 -> add functions 
function makeSound(animal) {
    const tasks = {
        dog() {
            console.log('siru');
        },
        cat() {
            console.log('kitty');
        },
        bird() {
            console.log('huhu');
        }
    }
    if (!tasks[animal]) {
        console.log('...?');
        return;
    }
    tasks[animal]();
}
makeSound('dog');
makeSound('bird');

cf. https://learnjs.vlpt.us/basics/04-conditions.html