TypeScript 初探

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基本类型

  • boolean:
    1
    let done: boolean = true
  • number:
    1
    let count: number = 20
  • string:
    1
    let name = "Edward Wang"
  • array:
    1
    2
    let list1: number[] = [1, 2, 3]
    let list2: Array<number> = [1, 2, 3]
  • tuple:
    1
    let x: [string, number] = ["test", 2]
  • enum:
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    enum NUMBER {
      ONE,
      TWO,
      THREE,
    }
    let a = NUMBER.TWO
    let title: string = NUMBER[3]

  • any:

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    2
    3
    4
    let x: any = 4
    x = "string"

    let list: any[] = [1, true, "string"]

  • void:
    表示没有返回类型，只能被赋予 null 和 undefined。

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    function warning(): void {
      console.log("warning")
    }
    let unusable: void = undefined

  • null & undefined:
    默认情况下 null 和 undefined 是所有类型的子类型。如果使用了--strictNullChecks标记,null、undefined、void 只能赋值给他们自己。

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    2
    let u: undefined = undefined
    let n: null = null

  • never:
    表示永不存在值的类型。

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    function error(message: string): never {
      throw new Error(message)
    }

  • object:
    除 number、string、boolean、symbol、null 或 undefined 之外的类型。

类型断言

  • <>断言
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    2
    let text: any = "some text"
    let strLength = (<string>text).length
  • as 断言
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    2
    let text: any = "some text"
    let strLength = (text as string).length