Microsoft/TypeScript

Intl.NumberFormat does not model required properties when `style` is set to `currency`

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#57,514 opened on Feb 23, 2024

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BugDomain: lib.d.tsHelp Wanted

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Description

⚙ Compilation target

ESNext

⚙ Library

ESNext

Missing / Incorrect Definition

According to the MDN docs, when style is set to currency, then the currency property must be provided.

This could be achieved through a discriminating union on the style property e.g.

interface NumberFormatParamsStyleDecimal {
    style: "decimal"
}

interface NumberFormatParamsStyleCurrency {
    style: "currency"
    currency: string
}

type NumberFormatParams = NumberFormatParamsStyleDecimal | NumberFormatParamsStyleCurrency;

const numberFormat = (params: NumberFormatParams) => {};

numberFormat({
    style: "decimal",
})

numberFormat({
    style: "currency",
    currency: "USD"
})

Sample Code

This fails at runtime, but does not fail compilation:

new Intl.NumberFormat("en", {
    style: "currency",
    currency: undefined
});

VM159:1 Uncaught TypeError: Currency code is required with currency style.
    at new NumberFormat (<anonymous>)
    at <anonymous>:1:1

Documentation Link

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat#style

Contributor guide

Research direction
Inspect the current type definitions for Intl.NumberFormatOptions and add a discriminated union to enforce required currency property when style is 'currency'.
Tech stack
typescript
Domain
frontend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
TypeScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75