In typescript global types can be declared in a .d.ts file and used anywhere without explicitly importing them. Our project's .d.ts file is named project.d.ts.
project.d.ts
It contains:
Some library types in the form of [triple slash directives](https: //www.typescriptlang.org/docs/handbook/triple-slash-directives.html). These need to be placed at the top of the file.
Some library module declarations (usually these are included because these libs don't have typings but we still need to use them).
Our own global types.
Typescript provides many [Utility Types](https: //www.typescriptlang.org/docs/handbook/utility-types.html) which are useful for manipulating the base types in the global ComponentTypes interface.
Utility Types
TypeScript: Documentation - Utility Types
Excerpt
Types which are globally included in TypeScript
TypeScript provides several utility types to facilitate common type transformations. These utilities are available globally.
A few basic ones to know:
Pick<Type, Keys>
Only use the specified Keys from the Type.
Partial<Type>
Allows the type to be optional (undefined)
Required<Type>
Opposite of Partial, the type must be defined
Using the stategies above you can select types from the global source and compose them to create a representation of the props in a specific component. While the global types live in project.d.ts, component level types should generally be placed in a types.ts file within the component directory and imported for use.
Although ComponentTypes is a✅ _Good starting place, some components may require a type that is more specific and not usefully included in the global declaration._
Naming
class
🧑🔬 PascalCase
🚫 Bad
✅ Good
For memebers/methods use 🐪 camelCase
🚫 Bad
✅ Good
enum
🧑🔬 PascalCase
🚫 Bad
✅ Good
interface
🧑🔬 PascalCase
🚫 Bad
✅ Good
For memebers use 🐪 camelCase
🚫 Bad
✅ Good
namespace
🧑🔬 PascalCase
🚫 Bad
✅ Good
type
🧑🔬 PascalCase
🚫 Bad
✅ ✅ Good
variable and function
🐪 camelCase
🚫 Bad
✅ Good
React | Typescript | Tailwind | Forms | Unit Tests
constructs a type consisting of all properties of Type set to required. The opposite of [Partial](https: //www.typescriptlang.org/docs/handbook/utility-types.html#partialtype).
constructs a type with all properties of Type set to readonly, meaning the properties of the constructed type cannot be reassigned.
Example
This utility is useful for representing assignment expressions that will fail at runtime (i.e. when attempting to reassign properties of a [frozen object](https: //developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze)).
constructs an object type whose property keys are Keys and whose property values are Type. This utility can be used to map the properties of a type to another type.
constructs a tuple or array type from the types of a constructor function type. It produces a tuple type with all the parameter types (or the type never if Type is not a function).
Extracts the type of the [this](https: //www.typescriptlang.org/docs/handbook/functions.html#this-parameters) parameter for a function type, or [unknown](https: //www.typescriptlang.org/docs/handbook/release-notes/typescript-3-0.html#new-unknown-top-type) if the function type has no this parameter.
Removes the [this](https: //www.typescriptlang.org/docs/handbook/functions.html#this-parameters) parameter from Type. If Type has no explicitly declared this parameter, the result is simply Type. Otherwise, a new function type with no this parameter is created from Type. Generics are erased and only the last overload signature is propagated into the new function type.
This utility does not return a transformed type. Instead, it serves as a marker for a contextual [this](https: //www.typescriptlang.org/docs/handbook/functions.html#this) type. Note that the [noImplicitThis](https: //www.typescriptlang.org/tsconfig#noImplicitThis) flag must be enabled to use this utility.
Example
In the example above, the methods object in the argument to makeObject has a contextual type that includes ThisType<D & M> and therefore the type of [this](https: //www.typescriptlang.org/docs/handbook/functions.html#this) in methods within the methods object is { x: number, y: number } & { moveBy(dx: number, dy: number): number }. Notice how the type of the methods property simultaneously is an inference target and a source for the this type in methods.
The ThisType<T> marker interface is simply an empty interface declared in lib.d.ts. Beyond being recognized in the contextual type of an object literal, the interface acts like any empty interface.
Intrinsic String Manipulation Types
Uppercase<StringType>
Lowercase<StringType>
Capitalize<StringType>
Uncapitalize<StringType>
To help with string manipulation around template string literals, TypeScript includes a set of types which can be used in string manipulation within the type system. You can find those in the [Template Literal Types](https: //www.typescriptlang.org/docs/handbook/2/template-literal-types.html#uppercasestringtype) documentation.
tsinterface Props { a?: number; b?: string;}
const obj: Props = { a: 5 };
const obj2: Required<Props> = { a: 5 };Property 'b' is missing in type '{ a: number; }' but required in type 'Required<Props>'.2741Property 'b' is missing in type '{ a: number; }' but required in type 'Required<Props>'.Try
tsinterface Todo { title: string;}
const todo: Readonly<Todo> = { title: "Delete inactive users",};todo.title = "Hello";Cannot assign to 'title' because it is a read-only property.2540Cannot assign to 'title' because it is a read-only property.Try
tstype T0 = Exclude<"a" | "b" | "c", "a">; type T0 = "b" | "c"type T1 = Exclude<"a" | "b" | "c", "a" | "b">; type T1 = "c"type T2 = Exclude<string | number | (() => void), Function>; type T2 = string | numberTry
tstype T0 = Extract<"a" | "b" | "c", "a" | "f">; type T0 = "a"type T1 = Extract<string | number | (() => void), Function>; type T1 = () => voidTry
tstype T0 = NonNullable<string | number | undefined>; type T0 = string | numbertype T1 = NonNullable<string[] | null | undefined>; type T1 = string[]Try
tsdeclare function f1(arg: { a: number; b: string }): void;type T0 = Parameters<() => string>; type T0 = []type T1 = Parameters<(s: string) => void>; type T1 = [s: string]type T2 = Parameters<<T>(arg: T) => T>; type T2 = [arg: unknown]type T3 = Parameters<typeof f1>; type T3 = [arg: {
a: number;
b: string;
}]type T4 = Parameters<any>; type T4 = unknown[]type T5 = Parameters<never>; type T5 = nevertype T6 = Parameters<string>;Type 'string' does not satisfy the
constraint '(...args: any) => any'.2344Type 'string' does not satisfy the
constraint '(...args: any) => any'. type T6 = nevertype T7 = Parameters<Function>;Type 'Function' does not satisfy the
constraint '(...args: any) => any'.
Type 'Function' provides no match for the signature '(...args: any): any'.2344Type 'Function' does not satisfy the
constraint '(...args: any) => any'.
Type 'Function' provides no match for the signature '(...args: any): any'. type T7 = neverTry
tstype T0 =
constructorParameters<Error
constructor>; type T0 = [message?: string]type T1 =
constructorParameters<Function
constructor>; type T1 = string[]type T2 =
constructorParameters<RegExp
constructor>; type T2 = [pattern: string | RegExp, flags?: string]type T3 =
constructorParameters<any>; type T3 = unknown[]type T4 =
constructorParameters<Function>;Type 'Function' does not satisfy the
constraint 'abstract new (...args: any) => any'.
Type 'Function' provides no match for the signature 'new (...args: any): any'.2344Type 'Function' does not satisfy the
constraint 'abstract new (...args: any) => any'.
tsdeclare function f1(): { a: number; b: string };type T0 = ReturnType<() => string>; type T0 = stringtype T1 = ReturnType<(s: string) => void>; type T1 = voidtype T2 = ReturnType<<T>() => T>; type T2 = unknowntype T3 = ReturnType<<T extends U, U extends number[]>() => T>; type T3 = number[]type T4 = ReturnType<typeof f1>; type T4 = {
a: number;
b: string;
}type T5 = ReturnType<any>; type T5 = anytype T6 = ReturnType<never>; type T6 = nevertype T7 = ReturnType<string>;Type 'string' does not satisfy the
constraint '(...args: any) => any'.2344Type 'string' does not satisfy the
constraint '(...args: any) => any'. type T7 = anytype T8 = ReturnType<Function>;Type 'Function' does not satisfy the
constraint '(...args: any) => any'.
Type 'Function' provides no match for the signature '(...args: any): any'.2344Type 'Function' does not satisfy the
constraint '(...args: any) => any'.
Type 'Function' provides no match for the signature '(...args: any): any'. type T8 = anyTry
tsclass C { x = 0; y = 0;}type T0 = InstanceType<typeof C>; type T0 = Ctype T1 = InstanceType<any>; type T1 = anytype T2 = InstanceType<never>; type T2 = nevertype T3 = InstanceType<string>;Type 'string' does not satisfy the
constraint 'abstract new (...args: any) => any'.2344Type 'string' does not satisfy the
constraint 'abstract new (...args: any) => any'. type T3 = anytype T4 = InstanceType<Function>;Type 'Function' does not satisfy the
constraint 'abstract new (...args: any) => any'.
Type 'Function' provides no match for the signature 'new (...args: any): any'.2344Type 'Function' does not satisfy the
constraint 'abstract new (...args: any) => any'.
Type 'Function' provides no match for the signature 'new (...args: any): any'. type T4 = anyTry