MediumModern JS💻 Output Question

Logical assignment operators

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Hint

??= assigns only if null/undefined. ||= if falsy. &&= only if truthy. They short-circuit.

What does this output?

let a = null;
let b = 0;
let c = 'existing';
a ??= 'default';
b ||= 'fallback';
c &&= 'updated';
console.log(a);
console.log(b);
console.log(c);

default
fallback
updated

Explanation: a??=: null, so assign. b||=: 0 is falsy, so assign. c&&=: truthy, so assign.

Key Insight: ??= assigns only if null/undefined. ||= if falsy. &&= only if truthy. They short-circuit.