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Fundamentals · easy

8. Truthiness and Nullish Handling

Falsy values, ?? and ?.

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Falsy values are `false`, `0`, `-0`, `0n`, `""`, `null`, `undefined`, and `NaN`. Nullish coalescing (`??`) only falls back on `null` or `undefined`.

js
const gas = input ?? 21000;      // preserves input if 0
const rpc = cfg?.network?.rpc;   // safe optional chain

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  1. 1. Which operator keeps a valid 0?

  2. 2. Is empty string "" falsy?

  3. 3. What does a?.b return if a is null?

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