Narrowing & Guards interview questions

1. A.narrowing a value to a class type using the instanceof operator
2. B.a union of object types sharing a literal tag property that the compiler uses to narrow between them
3. C.narrowing by checking whether a given property key exists on an object
4. D.refining a broader type to a more specific one within a particular code branch

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1. A.Type narrowing
2. B.in operator guard
3. C.User-defined type guard
4. D.Discriminated union

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1. A.Type narrowing — narrowing a union by checking a value's primitive type with typeof
2. B.Type narrowing — a union of object types sharing a literal tag property that the compiler uses to narrow between them
3. C.Type narrowing — narrowing by checking whether a given property key exists on an object
4. D.Type narrowing — refining a broader type to a more specific one within a particular code branch

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1. A.narrowing by checking whether a given property key exists on an object
2. B.narrowing a value to a class type using the instanceof operator
3. C.a union of object types sharing a literal tag property that the compiler uses to narrow between them
4. D.narrowing a union by checking a value's primitive type with typeof

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1. A.instanceof guard
2. B.typeof guard
3. C.in operator guard
4. D.Type narrowing

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1. A.typeof guard — refining a broader type to a more specific one within a particular code branch
2. B.typeof guard — narrowing a union by checking a value's primitive type with typeof
3. C.typeof guard — narrowing a value to a class type using the instanceof operator
4. D.typeof guard — a union of object types sharing a literal tag property that the compiler uses to narrow between them

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1. A.refining a broader type to a more specific one within a particular code branch
2. B.narrowing a value to a class type using the instanceof operator
3. C.narrowing a union by checking a value's primitive type with typeof
4. D.a function whose return type is arg is T, telling the compiler the argument is a specific type

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1. A.typeof guard
2. B.Type narrowing
3. C.instanceof guard
4. D.Discriminated union

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1. A.instanceof guard — a union of object types sharing a literal tag property that the compiler uses to narrow between them
2. B.instanceof guard — a function whose return type is arg is T, telling the compiler the argument is a specific type
3. C.instanceof guard — narrowing a value to a class type using the instanceof operator
4. D.instanceof guard — narrowing a union by checking a value's primitive type with typeof

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1. A.narrowing a union by checking a value's primitive type with typeof
2. B.narrowing a value to a class type using the instanceof operator
3. C.a function whose return type is arg is T, telling the compiler the argument is a specific type
4. D.narrowing by checking whether a given property key exists on an object

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1. A.instanceof guard
2. B.in operator guard
3. C.typeof guard
4. D.User-defined type guard

Answer + AI explanation with Pro

1. A.in operator guard — narrowing a union by checking a value's primitive type with typeof
2. B.in operator guard — narrowing by checking whether a given property key exists on an object
3. C.in operator guard — refining a broader type to a more specific one within a particular code branch
4. D.in operator guard — narrowing a value to a class type using the instanceof operator

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1. A.a function whose return type is arg is T, telling the compiler the argument is a specific type
2. B.narrowing a value to a class type using the instanceof operator
3. C.a union of object types sharing a literal tag property that the compiler uses to narrow between them
4. D.narrowing a union by checking a value's primitive type with typeof

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1. A.instanceof guard
2. B.in operator guard
3. C.User-defined type guard
4. D.Discriminated union

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1. A.Discriminated union — a union of object types sharing a literal tag property that the compiler uses to narrow between them
2. B.Discriminated union — refining a broader type to a more specific one within a particular code branch
3. C.Discriminated union — a function whose return type is arg is T, telling the compiler the argument is a specific type
4. D.Discriminated union — narrowing a value to a class type using the instanceof operator

Answer + AI explanation with Pro

1. A.a union of object types sharing a literal tag property that the compiler uses to narrow between them
2. B.narrowing a union by checking a value's primitive type with typeof
3. C.a function whose return type is arg is T, telling the compiler the argument is a specific type
4. D.narrowing a value to a class type using the instanceof operator

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1. A.instanceof guard
2. B.Discriminated union
3. C.in operator guard
4. D.User-defined type guard

Answer + AI explanation with Pro

1. A.User-defined type guard — narrowing a union by checking a value's primitive type with typeof
2. B.User-defined type guard — a function whose return type is arg is T, telling the compiler the argument is a specific type
3. C.User-defined type guard — a union of object types sharing a literal tag property that the compiler uses to narrow between them
4. D.User-defined type guard — narrowing a value to a class type using the instanceof operator

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