➕strict equality (===)

equality without type conversion.

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

compares two values, without type conversion.

🈯 synonyms： ”identity operator"

🗺️ 圖表

• 👉 compare： sloppy equality (==)

⭐️ 重點

<= and >= do not rely on == or ===❗

the comparison between switch (expr) and a case clause is done by "===".

💈範例

• replit： strict equality (===)

// (different types)
null === undefined,  // false
0    === '0',        // false
0    === false,      // false
1    === true,       // false
'1'  === true,       // false
'0'  === false,      // false 

// (same type, different instannces)
Symbol() === Symbol(),    // false (different symbols)
{a: 1} === {a: 1},        // false (different objects)

// ⭐️ computer math is not perfect!
0.1 + 0.2,           // 0.30000000000000004
0.1 + 0.2 === 0.3,   // false❗ 

👥 相關

• sloppy equality (==)

• assignment (=)

• n.isEqual()

• primitive

📗 參考

• JavaScript: The Definitive Guide ⟩

  • 3.9.1 Conversions & Equality

  • 4.9.1 Equality and Inequality Operators ⭐️

📘 手冊

• Strict equality (===)