parseInt

parseInt - > 문자데이터 숫자로 전환

삼항연산자

var age = 20;
var result = age >= 20? "성인":"미성년";
console.log(result);

age>=20? console.log("성인"): console.log("미성년");

조건 ?참일 때 실행: 거짓일 때 실행

<!-- 테일윈드 -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/tailwindcss/2.2.19/tailwind.min.css">

<!-- 제이쿼리 -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>

<div class="box-1">
    <span class="box-1__minus">-</span>
    <span class="box-1__num">0</span>
    <span class="box-1__plus">+</span>
</div>

body {
    margin: 0;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.box-1 {
    border: 10px solid black;
    padding: 20px;
    font-size: 2rem;
    font-weight: bold;
    user-select: none;
}

.box-1__minus,
.box-1__plus {
    cursor: pointer;
}

console.clear();

function Box1__init() {
    $(".box-1__minus").click(function () {
        const num = parseInt($(".box-1__num").text());
        const newNum = num - 1 >= 0 ? num - 1 : 0;
        $(".box-1__num").text(newNum);
    });

    $(".box-1__plus").click(function () {
        const maxNum = 5;
        const num = parseInt($(".box-1__num").text());
        const newNum = num + 1 <= maxNum ? num + 1 : maxNum;
        $(".box-1__num").text(newNum);
    });
}

Box1__init();