Default value for each type in typescript

Question

Where can I find the default value of each type in typescript? For example, where is mentioned the default value for number type is null or 0.? Or about the string?

The default value means the value of a variable that is defined, but not assigned. Like let a : number;. This happens a lot in object definitions. For example:

 class A{
     let a: number;
     let b: string;
 }
 let obj: A;

Therefore, the question is on the values of a and b for obj.

Answer 1

The default value of every type is undefined

From: MDN - 'undefined'

A variable that has not been assigned a value is of type undefined.

For example, invoking the following will alert the value 'undefined', even though greeting is of type String

let greeting: string;
alert(greeting);