TypeScript uses ‘<>’ to surround casts, so the above becomes: var script = <HTMLScriptElement>document.getElementsByName(“script”)[0]; However, unfortunately you cannot do: var script = (<HTMLScriptElement[]>document.getElementsByName(id))[0]; You get the error Cannot convert ‘NodeList’ to ‘HTMLScriptElement[]’ But you can do : (<HTMLScriptElement[]><any>document.getElementsByName(id))[0];
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
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
6 June 2022 UPDATE TS 4.8 Since TypeScript 4.8, it is possible without numeric union hack. See PR //in my code type ParseInt<T extends `text${number}`> = T extends any ? (T extends `text${infer Digit extends number}` ? Digit : never) : never // 0 | 1 | 2 | 3 | 4 type Result = … Read more
The discussion in issue Microsoft/TypeScript#14094 is relevant here. Types in TypeScript are open in the sense that an object has to have at least the properties described by a type for it to match. So the object { value: 7, data: ‘test’, note: ‘hello’ } matches the type { value: number, data: string }, even … Read more
2019 Update The current answers and the official documentation are outdated. And for those new to TypeScript, the terminology used isn’t clear without examples. Below is a list of up-to-date differences. 1. Objects / Functions Both can be used to describe the shape of an object or a function signature. But the syntax differs. Interface … Read more