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Table of Contents
|| (Logical OR) vs ?? (Nullish Coalescing) vs && (Logical AND)
The ||, ??, and && operators are used to perform different types of logical operations.
|| (Logical OR)
The || operator returns the first truthy value it encounters or the last value if none are truthy:
const a = 0; const b = 'hello'; const result = a || b; // 'hello'
?? (Nullish Coalescing)
The ?? operator returns the right-hand operand when the left-hand operand is null or undefined, and the left-hand operand otherwise.
It's useful for providing default values:
const a = undefined; const b = 'default'; const result = a ?? b; // 'default'
&& (Logical AND)
The && operator returns the first falsy value it encounters or the last value if all are truthy:
const a = 'hello'; const b = 42; const result = a && b; // 42
Comparison
|| is generally used for providing a fallback value when dealing with falsy values (false, 0, empty strings, null, undefined, NaN).
?? is more specific than || because it only falls back for null or undefined, not for other falsy values like 0 or an empty string ''.
&& is used to ensure that multiple conditions are truthy.
Example:
const value = 0; const fallback1 = 'fallback'; const result1 = value || fallback1; // 'fallback' because 0 is falsy const result2 = value ?? fallback1; // 0 because 0 is not null or undefined const result3 = value && fallback1; // 0 because 0 is the first value, and it's falsy