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JavaScriptIntermediate#es6#operators

What is optional chaining and nullish coalescing?

?. short-circuits to undefined instead of throwing when a link in the chain is null or undefined. ?? returns the right side only when the left is null or undefined, unlike || which also replaces 0 and ''.

Example
user?.address?.city;   // undefined, no crash
const port = cfg.port ?? 3000; // keeps 0 if given
const bad = cfg.port || 3000;  // 0 becomes 3000

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