Undefined property on an object

Issue

I have a Typescript project in which I am reassigning variables depending on the value that the object contains.

What I am trying to do is define a variable from a property of the object, instead, if this property does not exist, a default value is established.

This is my Object:

interface InsParams {
  host?: string,
  country?: string,
  pageLimit?: number,
  pageOffset?: number,
  pageToken?: string
}

let dataObj: InsParams;

This is the variable I'm creating:

let limit: number = dataObj.pageLimit ? dataObj.pageLimit : 1000

This is the error it shows:

Error: Cannot read properties of undefined

My problem: I need if the property does not exist to assign another value to the limit variable, but it shows an error.

Solution

Your issue comes from dataObj being potentially undefined. In this case, you can use optional chaining + null coalescing operator:

let limit = dataObj?.pageLimit ?? 1000;

Answered By - Terry