What is the time and space complexity of typeof vs instanceof?

Time complexity: O(1). Space complexity: O(1).

typeof vs instanceof

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Solution Guide: typeof vs instanceof

Approach

Compare typeof (returns a string for primitive types and "object"/"function" for references) with instanceof (walks the prototype chain). Highlight the classic gotchas: typeof null returns "object", typeof [] returns "object", and show Array.isArray as the reliable array check.

Complexity Analysis

Time: O(1)
Space: O(1)

Pattern

Type Checking Patterns

Why It Works

typeof operates on the internal type tag of a value (with the null bug being a legacy spec issue), while instanceof relies on the prototype chain. Neither alone covers all cases, so combining them or using Array.isArray is necessary.

Updated Mar 2026