💍falsy

only 7 "falsy" values in JS.

JS ⟩ value ⟩ type ⟩ conversion ⟩ falsy

7 falsy values：(converts to false)

• false, 0, 0n, null, undefined, NaN, "" (empty string).

any other value is "truthy", and converts to true.

⭐️ 重點

every value is either truthy or falsy❗

all objects are truthy (convert to true).

operator(s) that expect boolean operands will work with an operand of any type❗

👥 相關

• Boolean

• arr.filter() - remove falsy values.

💈範例

'0' == false                // true❗️
if ('0') console.log('hi')  // hi  (⭐️ '0' is truthy❗️)

'0' === false               // false❗️

// facts about empty array
[] == ![]                   // true❗️
[] == []                    // false❗️
Boolean([])                 // true
Boolean(![])                // false❗️

📗 參考

• sitepoint ⟩ Truthy and Falsy: When All is Not Equal in JavaScript

🗣 討論

• In JavaScript, why is "0" equal to false, but when tested by 'if' it is not false by itself?