TypeScript

声明数组的三种方式

• let array1: string[] = ['name', 'age'];
• let array2: Array<string> = ['name', 'age'];
• let array3: [string] = ['name', 'age']; (推荐)
• let array4: [string, number] = ['name', 123];

声明枚举

enum Color {
    Red,
    Green,
    Blue = 5
};
let color1: Color = Color.Green; // print 1
let color2: Color = Color.Blue; // print 5
let colorName: string = Color[0]; // print Red

声明联合类型

let foo: string | number = 123;
foo = 'foo'; // 合法
foo = true; // 不合法

类型断言

let someValue: any = "this is a string";
let strLength: number = (someValue).length;

或者：（推荐）

let someValue: any = "this is a string";
let strLength: number = (someValue as string).length;