🌟nested default values

JS ⟩ operator ⟩ assignment ⟩ destructuring ⟩ nested default values

💈範例

• replit： nest default values

// ⭐ test cases
const opts = [
    {},
    { pad: {} },
    { pad: { length: 10 } },
    { pad: { length: 1, char: 'x' } },
];

// ⭐ destructuring arguments
function print({

    prefix = true,

    // ⭐ `pad` might be overridden❗
    pad = {
        length: 0,    // ⭐ nested default value
        char: '_',
    },

} = {}) {
    
    // ⭐ better destructure `pad` again❗
    const { length = 0, char = '_' } = pad;
    
    console.log(prefix, char, length, pad);
}

for (const opt of opts) {
    print(opt);
}

// P    C  L         pad
// -----------------------------------
// true _  0  { length: 0, char: '_' }
// true _  0  {}
// true _ 10  { length: 10 }
// true x  1  { length: 1, char: 'x' }

📗 參考

• JS.info ⟩ nested destructuring
• Ronald Chen ⟩ Destructuring Nested Objects
• Jay Cruz ⟩ How to Destructure Nested JavaScript Objects

👥 相關

• destructured parameter

• destructuring array

• object destructuring

⬇️ 應用

• n.toHex()

🗣 討論

• ES6 deep nested object destructuring
• Destructuring with nested objects and default values