Javascript 如何在 TypeScript 2 中转换为数组？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/39649994/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to cast to array in TypeScript 2?
提问by FlavorScape
I had some code that cast an object to type array (so I could use array functions on the object without compile errors).
我有一些代码将对象转换为数组类型（因此我可以在对象上使用数组函数而不会出现编译错误）。
var n = (result.data['value'] as []).map( (a)=>{
//..
});
But on upgrade to ts2, I get:
但是在升级到 ts2 时，我得到：
error TS1122: A tuple type element list cannot be empty.
错误 TS1122：元组类型元素列表不能为空。
Which is actually a syntax error, claiming you forgot a comma or value. So, how do I modify this cast to work correctly?
这实际上是一个语法错误，声称您忘记了逗号或值。那么，如何修改此演员表以使其正常工作？
I tried as [IMyType]and it worked, but I'd prefer not to specify type since I only need the array.prototypefunctions here... also, I don't think that's how you actually do it.
我试过了as [IMyType]，它奏效了，但我不想指定类型，因为我只需要array.prototype这里的函数......而且，我认为这不是你实际这样做的方式。
回答by Nitzan Tomer
For some reason the compiler thinks that result.data['value']is a tupleand not an array.
出于某种原因，编译器认为这result.data['value']是一个元组而不是一个数组。
You can cast it like this:
你可以这样投射：
result.data['value'] as any[]
Which should tell the compiler that it's an array, or:
这应该告诉编译器它是一个数组，或者：
result.data['value'] as Array<any>
If your array has only items of type IMyTypethen simply:
如果您的数组只有类型的项目，IMyType那么只需：
result.data['value'] as IMyType[]
However, if your array contains items of different types then it's either a any[]or a tuple, for example:
但是，如果您的数组包含不同类型的项目，那么它要么是any[]一个元组，要么是一个元组，例如：
result.data['value'] as [IMyType, string, string]
In any case, in the compiled js it will be an array, but tuples let you define a fixed length arrays with specific types.
在任何情况下，在编译后的 js 中它将是一个数组，但是元组允许您定义具有特定类型的固定长度数组。
回答by chrisbajorin
You're not casting to an array.
你没有投射到一个数组。
[string]is a tuple with a single element string.
[string]是一个具有单个元素的元组string。
[string, string]is a tuple with two elements, stringand string.
[string, string]是一个有两个元素的元组，string和string。
[]is a tuple with zero elements.
[]是一个元素为零的元组。
The syntax for an array of strings is string[]
字符串数组的语法是 string[]
What you likely want is result.data['value'] as any[].
您可能想要的是result.data['value'] as any[].
回答by Gorka Hernandez
Alternatively to the previous cast syntax options mentioned above, you can also do the following:
除了上面提到的先前的强制转换语法选项，您还可以执行以下操作：
var n = (<SampleType[]>result.data['value']).map((a) => {
//..
});
