3 Ways to fix Property '..' has no initializer and is not definitely assigned in the constructor.ts

Let’s say you have following Person class written in Typescript

class Person {
  name: string
}

With name keyword underlined in red color, VSCode gives following warning

Property name has no initializer and is not definitely assigned in the constructor.ts

It is because TypeScript 2.7 includes a strict class checking where all the properties should be initialized in the constructor.

How do we fix this?

Approach 1

Set name property to empty string

class Person {
  name: string = ''
}

Approach 2

If the variable is passed as input while instantiating class, you can initialize it inside constructor

class Person {
  constructor(name: string) {
    this.name = name
  }
  name: string
}

Approach 3

Add the ! as a postfix to the variable name as follows

class Person {
  name!: string
}

When you add an exclamation mark after variable/property name, you’re telling to TypeScript that you’re certain that value is not null or undefined.

You can also get rid of warning by setting strictPropertyInitialization: false inside tsconfig.json