CODEWITHSUNDEEP
typescript
user31415629
user31415629

Reputation: 1005

Rolling up data in Typescript

I have the following code I'm trying to run:

interface Datapoint {
    [key: string]: number
}

const props: Array<string> = ["a", "b", "c"]

const data: Array<Datapoint> = ...

const rolled_up: Datapoint = data.reduce(function(a: Array<Datapoint>, b: Array<Datapoint>){
  props.map(function(prop: string){
    a[prop] += b[prop]
  })
  return a
})

I want to roll up my data array into a single Datapoint, where the fields are added over the array for the given properties (props).

When I try and compile this, I get:

error TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.

on the line 

a[prop] += b[prop]

What am I doing wrong?

Upvotes: 0

Views: 180

Answers (2)

Robby Cornelissen
Robby Cornelissen

Reputation: 97282

The types for the arguments to your reduce() function are wrong. Should be:

const rolled_up: Datapoint = data.reduce(function(a: Datapoint, b: Datapoint){
  props.map(function(prop: string){
    a[prop] += b[prop]
  })
  return a
})

Upvotes: 1

user31415629
user31415629

Reputation: 1005

This issue was the types in my reduce function, they should have been:

function(a: Datapoint, b: Datapoint)

Upvotes: 0

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