<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    // 自减和自增一样

    let a = '5';
    a++; //++或--会强制变数字进行运算
    console.log(a); //>>6
    console.log(typeof a); //>>number
</script>
</body>
</html>