Is there any difference between what the TypeScript spec calls a type assertion:
var circle = <Circle> createShape("circle");
And the newer as
operator:
var circle = createShape("circle") as Circle;
Both of which are typically used for compile-time casting?
The difference is that as Circle
works in TSX files, but <Circle>
conflicts with JSX syntax. as
was introduced for this reason.
For example, the following code in a .tsx
file:
var circle = <Circle> createShape("circle");
Will result in the following error:
error TS17002: Expected corresponding JSX closing tag for 'Circle'.
However, as Circle
will work just fine.
Use as Circle
from now on. It's the recommended syntax.
From Wiki page: "What's new in TypeScript [1.6]":
New .tsx file extension and as operator TypeScript 1.6 introduces a new .tsx file extension. This extension does two things: it enables JSX inside of TypeScript files, and it makes the new as operator the default way to cast (removing any ambiguity between JSX expressions and the TypeScript prefix cast operator). For example: var x =
Success story sharing
var x = foo as any; var x: any = foo;