如何确定打字稿、数字数组或字符串数​​组中的变量类型？

Question

I have a variable like

const data = [];

In some places in my App, data looks like string array or number array

// data [1, 2, 3]
// data ["1", "2", "3"]

How can I get the type of this variable - type string array or number array ?

Answer 1

Yes you can type your variables with a single type

// type data as an array of strings
const data: string[] = [];

// type data as an array of numbers
const data: number[] = [];

// type data as an array of objects
const data: object[] = [];

If you want to use a mix of types in your array, you can type it as any . But this may not be a good practise.

const data: any[] = [];

For more information about type in typescript, look here: Basic type documentation

For defining array with multiple types, look here: https://stackoverflow.com/a/29382420/1934484

Answer 2

@Tomas Vancoillie has the right idea.

You can declare them with the : operator.

You can also infer the type with Array(), for example:

let myStringArray = Array<string>();

Answer 3

You can define your array like this the typescript compiler will only allow strings

const array: Array<string> = [];

or if you want to have strings and numbers define it like this

const array: Array<string | number> = [];

You can also define it this way

const array: string[] = [];
const array: (string | number)[] = [];

Answer 4

如果你只需要获取 中元素的类型，因为它们要么是string要么是number ，你可以只获取第一个元素的类型，因为所有其他元素都具有相同的类型：

typeof data[0] // string or number