LimeStreem LimeStreem - 1 year ago 50
TypeScript Question

Why there are 2 different syntax of casting in typescript?

As long as I know, there are 2 type of syntax to cast in Typescript.

  1. Just using
    to cast

    const a = <A>b;

  2. Using
    statement to cast

    const a = b as A;

I guess generated code of 1 or 2 is completely same.
And, there were no such a syntax to use
statement when I started to use Typescript. I guess
is new syntax in typescript.

But, there should be something reason to make new syntax. Why they needed these syntax? Is there something inconvenient if there was only 1 cast syntax?

Answer Source

As described here

Originally the syntax that was added was <foo>.

However there is an ambiguity in the language grammar when using <foo> style assertions in JSX:

var foo = <string>bar;

Therefore it is now recommended that you just use as foo for consistency.