What is “type '{}'”?

Question

In TypeScript, what exactly is type \'{}\' and how does it relate to other built-in types?

For example, the last line of the following example gives

Answer 1

As far as I know, {} casts directly to a hash map like usage. You can only use keyed properties, versus the dot notation.

var o:{} = {}

should be equivalent to

var o:{[key:string]:any} = {}

So

o.x = 5; //fails

But

o['x'] = 5; //succeeds