Step 3 / Select topic TypeScript Types Easy

What this bank covers

• Basic conditional type resolution
• Blocking distribution with a tuple
• infer in a conditional type
• Inferring a function return type
• Assigning to a resolved conditional type
• T keeps its narrow type in the true branch
• Nested conditional types
• boolean distributes as true | false
• readonly modifier in a mapped type
• optional modifier in a mapped type
• removing optionality with -?
• Record as a mapped type
• satisfying a mapped type over a key union
• missing and excess keys for a mapped type
• removing readonly with -readonly
• Mapped type over a literal union
• Cross product of placeholders
• Numeric placeholder matching
• A literal that fails the pattern
• The Uppercase intrinsic
• Capitalize inside a template
• boolean in a placeholder
• string is not assignable to a pattern
• Concatenating two literals
• Template literal type with Uppercase
• Distributing over never
• A union of arrays is stricter than an array of a union
• Dropping null and undefined by distribution
• No distribution when T is not naked
• boolean distributes as false | true
• Array covariance
• Covariant up, not down
• Return-type covariance
• readonly arrays one-way
• Property covariance
• Top and bottom types
• Tuples versus arrays
• Parameter count rules
• method parameter bivariance
• Overload resolution picks the matching signature
• satisfies keeps the expression's own type
• satisfies does not add the target's index signature
• satisfies on a function expression
• satisfies is a check, not a cast
• satisfies still runs excess property checks
• Annotation versus satisfies for index signatures
• Overload arity and argument types
• satisfies checks property types and completeness
• Overload resolution picks one signature
• Narrowing a discriminated union by throwing
• Indexed access on a discriminated union
• Only shared properties are readable before narrowing
• A union member needs its discriminant
• The discriminant itself narrows too
• Exhaustiveness checking with never
• A missed case breaks the never check
• Comparing a discriminant to a value outside the union
• A member is assignable to its union
• Literal inference under a string constraint
• Argument must satisfy the constraint
• Union constraint rejects outside members
• keyof constraint with indexed access return
• Default type argument with a constraint
• Constraints on type aliases
• Array constraint and inference
• Only constraint members are visible
• T is assignable to its constraint
• Indexing a tuple with number
• Recursive conditional type that flattens arrays
• Chained indexed access on a recursive interface
• Recursive JSON type alias
• Illegal direct self-reference in a union alias
• Recursive tuple recursion with infer
• keyof a string index signature
• Indexed access types as annotations
• Recursively unwrapping nested promises
• Chained indexed access types
• infer captures the first parameter type
• Mapped type value substitution
• Template literal types with Uppercase
• Distribution requires a naked type parameter
• Extract on a discriminated union
• Constrained key generic narrows the return type
• Inferring an array element type
• Inferring a function's return type
• When the infer pattern does not match
• Inferring a parameter type
• Where infer is allowed
• Unwrapping a Promise with infer
• Fallback branch returning T
• Inferring the first tuple element
• Tuple patterns and empty tuples
• Distributive conditional types filtering a union
• Disabling distribution with tuple wrapping
• Filtering unions with distributive conditionals