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In this article Xiaobian for you to introduce in detail "typescript utility type how to construct", the content is detailed, the steps are clear, the details are handled properly, I hope this article "typescript utility type how to construct" article can help you solve doubts, following the editor's ideas slowly in-depth, together to learn new knowledge.

Partial

Construct a type with all properties Type set to optional. This utility returns types that represent all subsets of a given type.

Interface Todo {

Title: string

Desc: string

}

Function updateTodo (todo: Todo, fieldsToUpdate: Partial) {

Return {... todo,... fieldsToUpdate}

}

Const todo1 = {

Title: 'organize desk'

Desc: 'clear clutter'

}

Const todo2 = updateTodo (todo1, {

Desc: 'throw out trash'

});

Required

Construct a type that consists of all the properties of Typeset to required

Interface Props {

A?: number

B?: string

}

Const obj: Props = {a: 5}

Const obj2: Required = {a: 5}

Readonly

Construct a type readonly with all properties set to Type, which means that properties of the construction type cannot be reassigned.

Interface Todo {

Title: string

}

Const todo: Readonly = {

Title: "Delete inactive users"

}

Todo.title = "Hello"

Record

Construct an object type with the property key Keys and the property value Type. This utility can be used to map attributes of one type to another.

Interface CatInfo {

Age: number

Breed: string

}

Type CatName = 'miffy' |' boris' | 'mordred'

Const cats: Record = {

Miffy: {age: 10, breed: 'Persian'}

Boris: {age: 5, breed: 'Maine Coon'}

Mordred: {age: 16, breed: 'British Shorthair'}

}

Pick

Construct a type Keys by selecting a set of attributes from the Type (string literals or union of string literals).

Interface Todo {

Title: string

Desc: string

Completed: boolean

}

Type TodoPreview = Pick

Const todo: TodoPreview = {

Title: 'clean room'

Desc: 'ddddd'

}

Omit

Construct a type by selecting all the attributes Type from it and then removing Keys (string literals or union of string literals).

Interface Todo {

Title: string

Description: string

Completed: boolean

CreatedAt: number

}

Type TodoPreview = Omit

Const todo: TodoPreview = {

Title: 'Clean room'

Completed: false

CreatedAt: 1615544252770

}

ReturnType

Construct a type Type that consists of the return type of function.

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