TypeScript - null versus undefined

Question

The TypeScript Coding Guidelines state

Use undefined. Do not use null

Having just read another article on ECMAScrip

Answer 1

Why use null over undefined?

In javascripts objects are dynamic without any type information. therefor:

var person
person.namme

could either be a misspell or it could be the name property. If you use undefined as null you won't know when debugging if:

• variable/property is not initialized yet, or
• you miss typed the property name.

Therefor null is preferable over undefined, you defer between:

• forgot to initialize property and
• wrong property used.

That said: Typescript is typed. thus the following code:

var person
person.namme

would result in a type error at compilation. Thus null in that sense is no longer needed.

That said, i still prefer null over undefined.