You can achieve what you want without the instanceof
keyword as you can write custom type guards now:
interface A{
member:string;
}
function instanceOfA(object: any): object is A {
return 'member' in object;
}
var a:any={member:"foobar"};
if (instanceOfA(a)) {
alert(a.member);
}
Lots of Members
If you need to check a lot of members to determine whether an object matches your type, you could instead add a discriminator. The below is the most basic example, and requires you to manage your own discriminators… you’d need to get deeper into the patterns to ensure you avoid duplicate discriminators.
interface A{
discriminator: 'I-AM-A';
member:string;
}
function instanceOfA(object: any): object is A {
return object.discriminator === 'I-AM-A';
}
var a:any = {discriminator: 'I-AM-A', member:"foobar"};
if (instanceOfA(a)) {
alert(a.member);
}