In JavaScript, many libraries use string arguments to change behavior. In this lesson we learn how Typescript catches string related errors at compile time by assigning a string literal as a type.
type whiteList = "DOG" | "CAT" | "BIRD"; function allowToTake(num: number, animal: whiteList): string{ return `You can bring ${num} ${animal}`; }
[TypeScript] Distinguishing between types of Strings in TypeScript
原文：http://www.cnblogs.com/Answer1215/p/5940758.html