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ViewsTypescript: how to define a object with many unknown keys
I'm building an application that access an API that returns an object with many unknown keys, each key represents an id of a user.
Example:
const response = {
"random id1": {name: "user1"},
"random id2": {name: "user2"},
...
"random id100": {name: "user100"}
}
I know that if I have just one unknown key I can define using something like:
type MyDefinition = {
[key: string]: Metadata
}
But how can I define an object with so many different keys?
3 answers
Answer question0
Extending @ASDFGerte comment. You can generate a range of numbers from 0 to 998 in typescript 4.5:
type MAXIMUM_ALLOWED_BOUNDARY = 999
type ComputeRange<
N extends number,
Result extends Array<unknown> = [],
> =
(Result['length'] extends N
? Result
: ComputeRange<N, [...Result, Result['length']]>
)
// 0 , 1, 2 ... 998
type NumberRange = ComputeRange<MAXIMUM_ALLOWED_BOUNDARY>[number]
type Name<T extends string> = { name: T }
type CustomResponse = {
[Prop in NumberRange]: Record<`random id${Prop}`, Name<`id${Prop}`>>
}
Here and here you can find an explanation of number range.
You have probable noticed that there is a limit you can't cross.
With above approach it will not allow random id1e4.
0
You can use a type defined with a template string like this:
const response: { [key: `random id${number}`]: { name: string }} = {
"random id1": {name: "user1"},
"random id2": {name: "user2"},
"random id100": {name: "user100"}
}
You can see it in action on this TypeScript playground.
0
[key: string] allows for any amount of unique strings as keys.
type Metadata = {
name: string
}
type MyDefinition = {
[key: string]: Metadata
}
const response: MyDefinition = {
"random id1": {name: "user1"},
"random id2": {name: "user2"},
// ...
"random id100": {name: "user100"},
};
Try it on TypeScript Playground