🔰comparison operator

<, >, <=, >= operators

JS ⟩ statement ⟩ expression ⟩ operator ⟩ relational ⟩ comparison

🗺️ 圖表

🧨 雷區

trichotomy law： a < b, a = b, a > b doesn't apply to NaN❗

3 <  NaN,      // false❗
3 == NaN,      // false❗
3 >  NaN,      // false❗

⭐️ 重點

comparison operators

• operands may be of any type.

• operands that are not numbers/strings are converted to numbers/strings.

• if either operand is (or converts to) NaN, the result is false. ⭐

comparison operators do allow to mix BigInt and Number❗

<= and >= do not rely on == or ===❗

• <= is defined to be "not >".

• >= is defined to be "not <".

with one exception, if either operand is NaN, the result is always false❗

👥 相關

• ℹ️ type conversion is involved in comparison.

• ℹ️ object -> primitive conversion is involved in comparison.

• ℹ️ comparison favors numbers, add/concate (+) favors strings.

💈範例

replit： comparison

 11  <  3,     // false    (numeric comparison)
'11' < '3',    // true     (string comparison)

// ⭐ "prefer-number" conversion
'11' <  3,     // false    ('11'  -> 11)

// ⭐ `NaN` always leads to `false`
'one' <  3,    // false    ('one' -> NaN)
'one' == 3,    // false    ('one' -> NaN)
'one' >  3,    // false    ('one' -> NaN)

// ⭐ trichotomy law： `a < b, a = b, a > b` doesn't apply to NaN❗
3 <  NaN,      // false
3 == NaN,      // false
3 >  NaN,      // false

📗 參考

• JavaScript: The Definitive Guide ⟩ 4.9.2 Comparison Operators

📘 手冊

• Less than (<)

• Greater than (>)

• Less than or equal (<=)

• Greater than or equal (>=)

• String.prototype.localeCompare() ⭐️ simply calls Intl.Collator

• Intl.Collator ⭐️ language-sensitive string comparison.