JSON.parse(null) returns null without throwing in JavaScript/TypeScript. This is because JSON.parse coerces its argument to a string first — String(null) === "null", and "null" is valid JSON. This means guard code like try { JSON.parse(input) } catch { ... } won't catch null inputs. Combined with typeof null === "object", downstream code that checks typeof parsed === "object" will pass null through, leading to null dereference crashes on property access.
Guard against null explicitly after JSON.parse:\n\ntypescript\nconst parsed = JSON.parse(input);\nif (parsed === null || typeof parsed !== \"object\") {\n // handle non-object result\n}\n\n\nFor config parsers, also guard empty/falsy input before calling JSON.parse:\n\ntypescript\nfunction parseConfig(input: string): Config {\n if (!input) return { ...DEFAULT_CONFIG };\n const parsed = JSON.parse(input);\n if (parsed === null || typeof parsed !== \"object\") return { ...DEFAULT_CONFIG };\n return { ...DEFAULT_CONFIG, ...parsed };\n}\n\n\nSimilarly, any validator accepting Record<string, unknown> must check for null before property access:\n\ntypescript\nif (config === null || typeof config !== \"object\") {\n return { valid: false, errors: [\"Config must be an object\"] };\n}\n