As defined in the Release Notes of TypeScript 2.9, if you keyof an interface with a string index signature it returns a union of string and number Given an object type X, keyof X is resolved as follows: If X contains a string index signature, keyof X is a union of string, number, and the … Read more
The only possible way this could work at compile time is if your arrays are tuples composed of literals. For example, here are some arrays with the same runtime values, but with different types in TypeScript: const tupleOfLiterals: [1, 2, 2] = [1, 2, 2]; const tupleOfNonLiterals: [number, number, number] = [1, 2, 2]; const … Read more
Generally event handlers should use e.currentTarget.value, e.g.: onChange = (e: React.FormEvent<HTMLInputElement>) => { const newValue = e.currentTarget.value; } You can read why it so here (Revert “Make SyntheticEvent.target generic, not SyntheticEvent.currentTarget.”). UPD: As mentioned by @roger-gusmao ChangeEvent more suitable for typing form events. onChange = (e: React.ChangeEvent<HTMLInputElement>)=> { const newValue = e.target.value; }
I use a method that first filters the fields and then combines them. reference Exclude property from type interface A { x: string } export type B = Omit<A, ‘x’> & { x: number }; for interface: interface A { x: string } interface B extends Omit<A, ‘x’> { x: number }
The compiler will not be able to understand that this is type safe because it generally does not reason very well about assignability for types that depend on as-yet-unspecified generic type parameters. There is an existing GitHub issue, microsoft/TypeScript#24085, that describes this situation. In fact, it is possible (but not very likely) that in your … Read more
After two years of TypeScript development, I’ve finally managed to solve this problem. Basically, TypeScript has two kind of module types declaration: “local” (normal modules) and ambient (global). The second kind allows to write global modules declaration that are merged with existing modules declaration. What are the differences between this files? d.ts files are treated … Read more
This is means that model field will have type :any and you will be able to assign anything to it. In this case model:any = {}; it declares new field model that contains empty object. To set an array you need to use model:Array = [];. You can also add type for your Array: model: … Read more