➕sloppy equality (==)

equality with type conversion.

JS ⟩ statement ⟩ expression ⟩ operator ⟩ relational ⟩ sloppy (==)

perform equality testing that allows type conversion.

🌟

🗺️ 圖表

• 👉 compare：strict equality (===)

⭐️ 重點

convertibility does not imply equality❗

// ⭐️ `undefined` can be converted to `false`.
undefined == false     // false❗ 

== never converts its operands to booleans❗

<= and >= do not rely on == or ===❗

💈範例

• replit： sloppy equality (==)

// ⭐️ sloppy equality (==)
null == undefined,  // true
0    == '0',        // true    ('0'   -> 0)
0    == false,      // true    (false -> 0)
1    == true,       // true    (true  -> 1)
'1'  == true,       // true    (true  -> 1, then '1' -> 1)
'0'  == false,      // true    (false -> 0, then '0' -> 0)

// ⭐️ convertibility doesn't imply equality
//   (undefined can be converted to false)
undefined == false, // false❗ 

👥 相關

• ⭐ type conversion

• 🌟

• n.isEqual()

• ℹ️ the following are involved in == operation.

  • strict equality (===)

  • object -> primitive conversion

• ⚖️ assignment (=)

📗 參考

• JavaScript: The Definitive Guide ⟩

  • 3.9.1 Conversions & Equality

  • 4.9.1 ⭐️