Javascript 如何在 Typescript 中创建一个空字符串数组？
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How can I make an empty string array in Typescript?
提问by
I would like to have an array that holds string error messages. Here's the code that I came up with:
我想要一个包含字符串错误消息的数组。这是我想出的代码：
var errors: [string];
errors = [];
Object.keys(response.data.modelState).forEach(function (key) {
errors.push.apply(errors, response.data.modelState[key]);
});
I tried some different ways to add a typescript definition to the variable errors but none seem to work for this case. The first definition works okay but then when I am pushing values I need to push to an array and when I set:
我尝试了一些不同的方法来向变量错误添加打字稿定义，但似乎没有一种方法适用于这种情况。第一个定义工作正常，但是当我推送值时，我需要推送到一个数组，当我设置时：
errors = [];
Then it gives me an error message:
然后它给了我一条错误消息：
Severity Code Description Project File Line Error TS2322 Type 'undefined[]' is not assignable to type '[string]'. Property '0' is missing in type 'undefined[]'. Severity Code Description Project File Line Error Build: Type 'undefined[]' is not assignable to type '[string]'.
严重性代码描述项目文件行错误 TS2322 类型“undefined[]”不可分配给类型“[string]”。类型“undefined[]”中缺少属性“0”。严重性代码描述项目文件行错误构建：类型“undefined[]”不可分配给类型“[string]”。
采纳答案by Radim K?hler
The definition of string arrayshould be:
字符串数组的定义应该是：
// instead of this
// var errors: [string];
// we need this
var errors: string[];
errors = [];
Note:another issue could be the parameter key here
注意：另一个问题可能是这里的参数键
...forEach(function (key) {...
I would guess that we often should declare two of them, because first is very often value, second key/index
我猜我们经常应该声明其中的两个，因为第一个通常是值，第二个是键/索引
Object.keys(response.data.modelState)
.forEach(function (value, key) {
errors.push.apply(errors, response.data.modelState[key]);
});
And even, we should use arrow function, to get the parent as this
甚至，我们应该使用箭头函数，将父级作为 this
Object.keys(response.data.modelState)
.forEach( (value, key) => {
errors.push.apply(errors, response.data.modelState[key]);
});
回答by Gero
Outside of a method:
在方法之外：
arr: string[] = [];
回答by Anders Zommarin
An alternative is to set the lengthto 0:
另一种方法是将 设置length为0：
const myArray = [1, 2, 3, 4]
myArray.length = 0
This makes it possible to use constin contexts where emptying the array is needed.
这使得可以const在需要清空数组的上下文中使用。
回答by wvdz
Missing an obvious answer, needed when not assigning it to a variable: [] as string[]
缺少一个明显的答案，在不将其分配给变量时需要： [] as string[]
