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Javascript – Typescript 'any' type error with dynamic array key

I’m getting the following error when trying to use a dynamic value for an array key.

Element implicitly has an 'any' type because expression of type '`faults_${string}`' can't be used to index type 'HeatsTable'.

export interface HeatsTable {
    heat_id: UUID
    start: number
    faults_1: string[]
    faults_2: string[]
    faults_3: string[]
    faults_4: string[]
  }

const fault = heatData[`faults_${runningId}`]; // Throws the above TS error

Using keyof HeatsTable works but causes an error on another page because it thinks faults could be a number. Is there another solution for this that I’m missing?

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2

Answers


  1. 0

    what if using this answer ?

    const fault = heatData[`faults_${runningId}` as keyof HeatsTable];
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  2. 0

    You could type runningId either manually or with extracting it from the type:

    Playground

    export interface HeatsTable {
    heat_id: string
    start: number
    faults_1: string[]
    faults_2: string[]
    faults_3: string[]
    faults_4: string[]
  }

declare const heatData: HeatsTable;
declare const runningId: number;

type RunningId = keyof {[K in keyof HeatsTable as K extends `faults_${infer A extends number}` ? A : never]: any}

const fault = heatData[`faults_${runningId as 1|2|3|4}`];
const fault2 = heatData[`faults_${runningId as RunningId }`];
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