# Booleans - Truthy & Falsy ``` 以下 6 個為 Falsy 其他都是 Truthy // Falsy false 0, -0 "" null undefined NaN // Truthy 'Hello World' 8 [], [1, 2, 3] {}, { name: 'leon' } function foo() {} true ... 可以用 !! 來做確認 !!"" // false !![] // true !!0 // false ```
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