35 lines
1.2 KiB
Plaintext
35 lines
1.2 KiB
Plaintext
The TypeScript type system offers a basic support for composite types:
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* _Union Types_ represent a value that can be one of the several types. They are constructed using a vertical bar (``++|++``) like the following ``++type NumberOrString = number | string++``.
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* _Intersection Types_ combine multiple types into one, so that the object of such type will have all the members of all intersection type elements. They are constructed using an ampersand (``++&++``) like the following ``++type SerializablePerson = Person & Serializable++``. Intersection Types are often used to represent mixins.
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Duplicating types when defining a union or interaction type makes the code less readable. Moreover duplicated types might be a simple mistake and another type should be used instead.
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== Noncompliant Code Example
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----
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function padLeft(value: string, padding: string | number | string) { // Noncompliant; 'string' type is used twice in a union type declaration
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// ...
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}
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function extend(p : Person) : Person & Person & Loggable { // Noncompliant; 'Person' is used twice
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// ...
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}
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----
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== Compliant Solution
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----
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function padLeft(value: string, padding: string | number | boolean) {
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// ...
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}
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function extend(p : Person) : Person & Loggable {
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// ...
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}
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----
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