How to access dynamically created properties of an object in typescript?

Question

I want to sort an array of objects with dynamically created properties. In the code block below, you can see that there are two errors thrown by typescript when I try to access this new properties.

I could initiate increaseData with an initial 0, but it does not seem like a good solution. How would you handle something like this in typescript normally?

Quick fix

let myData = {
        "myProp" : 0
    }

Original Code

let myNum = 0;
let myArray = []
let myData = {}
/** Code in between...
 * - pushes myData objects with a new property into myArray.
 * - result e.g.:
 *      myArray [
 *          {myProp : 5},
 *          {myProp : 4},
 *          {myProp : 5},
 *           ...
 *      ]
 */


// When myArray is filled with myData elements I want to sort them by myProp
    // ERROR: Property 'myProp' does not exist on type '{}'
let sortedArray = myArray.sort((a, b)=> (a.myProp < b.myProp) ? 1 : -1)
    // ERROR: Property 'myProp' does not exist on type '{}'
let result = sortedArray[0].myProp;

Answer 1

declare a type that has that property myProp

type HasProp = {
  myProp: number,
}

let myArray: HasProp[] = [];

// now Typescript will know that your array has object with `myProp` and it's a number
// note that pushing into that array must be for object with that prop already declared or else Typescript will point that out
// also note that each object with prop `myProp` is a valid object of type `HasProp`
myArray.sort((a, b)=> (a.myProp < b.myProp) ? 1 : -1);