parseInt: use more concrete type for `radix` argument

Search Terms

parseInt, radix

Suggestion

From MDN docs:
radix: An integer between 2 and 36 that represents the radix
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt#Parameters

TS definition (lib.es5.d.ts):

declare function parseInt(s: string, radix?: number): number;

It will be safer to use more concrete type for radix:

type TRadix =
2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|32|33|34|35|36

function safeParseInt(s: string, radix?: TRadix) {
  return parseInt(s, radix)
}

Use Cases

['1', '7', '11'].map(safeParseInt) // error -> Type 'number' is not assignable to type 'TRadix' ("strictFunctionTypes": true)

Examples

['1', '7', '11'].map(item) => safeParseInt(item, 10)) // OK

const config = {
  nested: {
    number: '42',
    radix: 10,
  },
} as const;
safeParseInt(config.nested.number, config.nested.radix)) // OK

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Start with the parseInt declaration in lib.es5.d.ts and review how its radix parameter is represented in the standard library definitions. Check the provided safeParseInt and map examples, then determine the type-level behavior and compatibility expectations that would define completion.