Typescript 中的 Array<Type> VS Type[]
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Array<Type> VS Type[] in Typescript
提问by dragonmnl
As far as I know a property's type can be defined in two ways when it's an Array.
据我所知，当它是一个数组时，可以通过两种方式定义属性的类型。
property_name: type
where type can be either
其中类型可以是
Array<string>, Array<MyType>, etc. (e.g. let prop1: Array<string>)
and
和
string[], MyType[], etc. (e.g. let prop1: string[])
What is the differencebetween the two cases? Or am I misunderstanding something (perhaps something about <> used in casting?)
这两种情况有什么区别？或者我误解了什么（也许是关于铸造中使用的 <> ？）
EDITsince the question is marked as duplicate, I am aware there is the other question about any[] but still I had a look at it before posting and to me it was more about the type 'any' than the different [] VS <> I asked
编辑，因为问题被标记为重复，我知道还有关于 any[] 的另一个问题，但在发布之前我仍然看过它，对我来说它更多的是关于类型“any”而不是不同的 [] VS < > 我问
回答by Paleo
There isn't any semantic difference
没有任何语义差异
There is no difference at all. Type[]is the shorthand syntaxfor an array of Type. Array<Type>is the generic syntax. They are completely equivalent.
完全没有区别。Type[]是数组的简写语法Type。Array<Type>是通用语法。它们是完全等效的。
The handbook provides an example here. It is equivalent to write:
function loggingIdentity<T>(arg: T[]): T[] {
console.log(arg.length);
return arg;
}
Or:
或者：
function loggingIdentity<T>(arg: Array<T>): Array<T> {
console.log(arg.length);
return arg;
}
And here is a quote from some release notes:
这是一些发行说明中的引用：
Specifically,
number[]is a shorthand version ofArray<number>, just asDate[]is a shorthand forArray<Date>.
具体而言，
number[]是的简写版Array<number>，就像Date[]是一个速记Array<Date>。
However, there is a case where the shorthand syntax is required
但是，有一种情况需要速记语法
Since TypeScript 3.4, there is a differencefor the new readonlytype modifier. Indeed:
从 TypeScript 3.4 开始，新的类型修饰符有所不同readonly。的确：
the
readonlytype modifier can only be used for syntax on array types and tuple types
该
readonly类型修饰符只能用于语法上数组类型和的元组类型
let err1: readonly Set<number>; // error!
let err2: readonly Array<boolean>; // error!
let okay: readonly boolean[]; // works fine
回答by Ozrix
foo: Array
means that it's a plain array, with an implicit anytype for it's members
意味着它是一个普通数组，any其成员具有隐式类型
foo: string[]
means that it's an array of strings, i.e. TypeScript will go mental if you try pushing anything other than strings into that array.
意味着它是一个字符串数组，也就是说，如果您尝试将字符串以外的任何内容推送到该数组中，TypeScript 会变心。
