typescript 2.0：具有默认值的参数(typescript 2.0: parameters with default values)

typescript 2.0：具有默认值的参数(typescript 2.0: parameters with default values)

地狱伙计们，

这是另一个打字稿2.0问题（启用了严格的空检查模式）。 因此，如果您定义一个具有所有参数的默认值的函数：

(name = "Luis", age = 40)=>void

然后所有参数都被认为是可选的，即，就好像我们有以下签名：

(name?: string, age?: number) => void

对？ 现在，当我们有这个签名时会发生什么：

(name = "Luis", age: number ) => void

根据VS代码，该签名与以下内容兼容：

(name: string, age: string) => void

现在，如果我激活严格的空检查模式，则以下调用不应该产生错误：

doIt(undefined, 30);

它编译好了，但如果我没错，undefined只会自动添加到可选参数类型列表中。 我没有找到任何默认初始化参数的引用。

所以，如果以前的电话没问题，有人可以指点我在官方文档中找到相关信息吗？

谢谢，

路易斯

Hell guys,

Here's another typescript 2.0 question (with strict null check mode enabled). So, if you define a function which has default values for all parameters:

(name = "Luis", age = 40)=>void

Then all parameters are considered optional, ie, it's as if we have the following signature:

(name?: string, age?: number) => void

Right? Now, what happens when we have this signature:

(name = "Luis", age: number ) => void

According to VS code, that signature is compatible with:

(name: string, age: string) => void

Now, if I activate the strict null check mode, shouldn't the following call produce an error:

doIt(undefined, 30);

It compiles ok, but if I'm not wrong, undefined will only get added automatically to the list of types of optional parameters. I haven't found any references to default initialized parameters.

So, if the previous call is ok, can someone point me to where I can find info about it in the official docs ?

Thanks,

Luis

最满意答案

快速注意：您不能仅在签名中指定默认值，例如以下是错误：

declare var foo: (name = "Luis", age = 40) => void; // ERROR: defaults only allowed in implementation

继续以下代码：

var foo = (name = "Luis", age: number) => null; foo(undefined, 123); foo(null, 123); // ERROR

显示该name与string或undefined兼容。 工具提示错误，但一般分析是正确的。

请随时通过https://github.com/Microsoft/TypeScript/issues提出问题

Quick note: You cannot specify defaults in just signatures e.g. the following is an error:

declare var foo: (name = "Luis", age = 40) => void; // ERROR: defaults only allowed in implementation

Continuing the following code:

var foo = (name = "Luis", age: number) => null; foo(undefined, 123); foo(null, 123); // ERROR

Shows that the name is compatible with string or undefined. The tooltip is wrong but the general analysis is correct.

Feel free to raise an issue at https://github.com/Microsoft/TypeScript/issues