blocks|key|2698173|text|按照documentation中的指定，使用undefined|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2698174|export+interface+INotificationService+{
++++error(message:+string,+title?:+string,+autoHideAfter?+:+number);
}

class+X+{
++++error(message:+string,+title?:+string,+autoHideAfter?:+number)+{
++++++++console.log(message,+title,+autoHideAfter);
++++}
}

new+X().error("hi+there",+undefined,+1000);|code-block|syntax|javascript|2698175|Playground+link。|2698176|entityMap|0|LINK|mutability|MUTABLE|url|https://www.typescriptlang.org/docs/handbook/2/functions.html#optional-parameters|1|http://www.typescriptlang.org/Playground#src=export%2520interface%2520INotificationService%2520{%2520%2520%2520%2520error(message:%2520string,%2520title?:%2520string,%2520autoHideAfter?%2520:%2520number);}class%2520X%2520{error(message:%2520string,%2520title?:%2520string,%2520autoHideAfter?:%2520number)%2520{console.log(message,%2520title,%2520autoHideAfter);}}new%2520X().error(^0|M|9|2|D|0|0|0|0|F|1|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|M|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]|U|$5|P|Q|R|E|$S|V]]]]

As specified in the <a href="https://www.typescriptlang.org/docs/handbook/2/functions.html#optional-parameters" rel="nofollow noreferrer">documentation</a>, use <code>undefined</code>:
<pre><code>export interface INotificationService {
 error(message: string, title?: string, autoHideAfter? : number);
}

class X {
 error(message: string, title?: string, autoHideAfter?: number) {
 console.log(message, title, autoHideAfter);
 }
}

new X().error(&quot;hi there&quot;, undefined, 1000);
</code></pre>
<a href="http://www.typescriptlang.org/Playground#src=export%20interface%20INotificationService%20%7B%0A%20%20%20%20error(message%3A%20string%2C%20title%3F%3A%20string%2C%20autoHideAfter%3F%20%3A%20number)%3B%0A%7D%0A%0Aclass%20X%20%7B%0A%09error(message%3A%20string%2C%20title%3F%3A%20string%2C%20autoHideAfter%3F%3A%20number)%20%7B%0A%09%09console.log(message%2C%20title%2C%20autoHideAfter)%3B%0A%09%7D%0A%7D%0A%0Anew%20X().error(%22hi%20there%22%2C%20undefined%2C%201000)%3B" rel="nofollow noreferrer">Playground link</a>.

blocks|key|2910197|text|不幸的是，在TypeScript中没有这样的东西(更多细节在这里：https://github.com/Microsoft/TypeScript/issues/467)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2910198|但是为了解决这个问题，你可以把你的params改成一个接口：|2910199|export+interface+IErrorParams+{
++message:+string;
++title?:+string;
++autoHideAfter?:+number;
}

export+interface+INotificationService+{
++error(params:+IErrorParams);
}

//then+to+call+it:
error({message:+'msg',+autoHideAfter:+42});|code-block|syntax|javascript|2910200|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/Microsoft/TypeScript/issues/467^0|X|1E|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

Unfortunately there is nothing like this in TypeScript (more details here: <a href="https://github.com/Microsoft/TypeScript/issues/467">https://github.com/Microsoft/TypeScript/issues/467</a>)

But to get around this you can change your params to be an interface:

<pre><code>export interface IErrorParams {
 message: string;
 title?: string;
 autoHideAfter?: number;
}

export interface INotificationService {
 error(params: IErrorParams);
}

//then to call it:
error({message: 'msg', autoHideAfter: 42});
</code></pre>

blocks|key|132938|text|另一种方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|132939|error(message:+string,+options?:+{title?:+string,+autoHideAfter?:+number});|code-block|syntax|javascript|132940|因此，当您想要省略title参数时，只需像这样发送数据：|132941|error('the+message',+{+autoHideAfter:+1+})|132942|我更喜欢这个选项，因为它允许我添加更多参数，而不必发送其他参数。|132943|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Another approach is:

<pre><code>error(message: string, options?: {title?: string, autoHideAfter?: number});
</code></pre>

So when you want to omit the title parameter, just send the data like that:

<pre><code>error('the message', { autoHideAfter: 1 })
</code></pre>

I'd rather this options because allows me to add more parameter without having to send the others.

blocks|key|132927|text|您可以通过?使用可选变量，或者如果您通过...有多个可选变量，则示例：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|132928|function+details(name:+string,+country="CA",+address?:+string,+...hobbies:+string)+{
++++//+...
}|code-block|syntax|javascript|132929|在上面的代码中：|132930|132931|name+is+required|unordered-list-item|132932|country是必需的，并且具有默认的value|132933|address+is+optional|132934|hobbies是可选参数的数组|132935|132936|entityMap^0|5|1|K|3|0|0|0|0|0|4|0|0|7|0|0|7|0|0|7|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|16|8|@]|D|@]|E|$]]|$1|N|3|O|5|P|7|17|8|@$9|18|A|19|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|P|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|S|3|T|5|P|7|1D|8|@$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|U|3|V|5|P|7|1G|8|@$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]|$1|X|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]]|Y|$]]

you can use optional variable by <code>?</code> or if you have multiple optional variable by <code>...</code>, example:

<pre><code>function details(name: string, country="CA", address?: string, ...hobbies: string) {
 // ...
}
</code></pre>

In the above: 

<ul>
<li><code>name</code> is required</li>
<li><code>country</code> is required and has a default value</li>
<li><code>address</code> is optional</li>
<li><code>hobbies</code> is an array of optional params</li>
</ul>

blocks|key|2910254|text|这与@Brocco的答案几乎相同，但略有不同：只在object.中传递可选参数(还使params对象成为可选的)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2910255|它最终有点像Python的**kwargs，但并不完全一样。|2910256|export+interface+IErrorParams+{
++title?:+string;
++autoHideAfter?:+number;
}

export+interface+INotificationService+{
++//+make+params+optional+so+you+don't+have+to+pass+in+an+empty+object
++//+in+the+case+that+you+don't+want+any+extra+params
++error(message:+string,+params?:+IErrorParams);
}

//+all+of+these+will+work+as+expected
error('A+message+with+some+params+but+not+others:',+{autoHideAfter:+42});
error('Another+message+with+some+params+but+not+others:',+{title:+'StackOverflow'});
error('A+message+with+all+params:',+{title:+'StackOverflow',+autoHideAfter:+42});
error('A+message+with+all+params,+in+a+different+order:',+{autoHideAfter:+42,+title:+'StackOverflow'});
error('A+message+with+no+params+at+all:');|code-block|syntax|javascript|2910257|entityMap^0|N|9|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

This is almost the same as @Brocco 's answer, but with a slight twist: only pass optional parameters in an object. (And also make params object optional).

It ends up being kind of like Python's **kwargs, but not exactly.

<pre><code>export interface IErrorParams {
 title?: string;
 autoHideAfter?: number;
}

export interface INotificationService {
 // make params optional so you don't have to pass in an empty object
 // in the case that you don't want any extra params
 error(message: string, params?: IErrorParams);
}

// all of these will work as expected
error('A message with some params but not others:', {autoHideAfter: 42});
error('Another message with some params but not others:', {title: 'StackOverflow'});
error('A message with all params:', {title: 'StackOverflow', autoHideAfter: 42});
error('A message with all params, in a different order:', {autoHideAfter: 42, title: 'StackOverflow'});
error('A message with no params at all:');
</code></pre>

blocks|key|2698192|text|您可以在接口上指定多个方法签名，然后在类方法上具有多个方法重载：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2698193|interface+INotificationService+{
++++error(message:+string,+title?:+string,+autoHideAfter?:+number);
++++error(message:+string,+autoHideAfter:+number);
}

class+MyNotificationService+implements+INotificationService+{
++++error(message:+string,+title?:+string,+autoHideAfter?:+number);
++++error(message:+string,+autoHideAfter?:+number);
++++error(message:+string,+param1?:+(string%7Cnumber),+param2?:+number)+{
++++++++var+autoHideAfter:+number,
++++++++++++title:+string;

++++++++//+example+of+mapping+the+parameters
++++++++if+(param2+!=+null)+{
++++++++++++autoHideAfter+=+param2;
++++++++++++title+=+<string>+param1;
++++++++}
++++++++else+if+(param1+!=+null)+{
++++++++++++if+(typeof+param1+===+"string")+{
++++++++++++++++title+=+param1;
++++++++++++}
++++++++++++else+{
++++++++++++++++autoHideAfter+=+param1;
++++++++++++}
++++++++}

++++++++//+use+message,+autoHideAfter,+and+title+here
++++}
}|code-block|syntax|javascript|2698194|现在，所有这些都将起作用：|2698195|var+service:+INotificationService+=+new+MyNotificationService();
service.error("My+message");
service.error("My+message",+1000);
service.error("My+message",+"My+title");
service.error("My+message",+"My+title",+1000);|2698196|...and+INotificationService的error方法将有以下选项：|offset|length|style|CODE|2698197|​|2698198|📷|atomic|2698199|2698200|Playground|2698201|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/279d8ef8206cee69b2e85e227a50f967.png|imageAlt|1|LINK|MUTABLE|url|http://www.typescriptlang.org/Playground/#src=interface%2520INotificationService%2520{%2520%2520%2520%2520error(message:%2520string,%2520title?:%2520string,%2520autoHideAfter?:%2520number);error(message:%2520string,%2520autoHideAfter:%2520number);}class%2520MyNotificationService%2520implements%2520INotificationService%2520{%2520%2520%2520%2520error(message:%2520string,%2520title?:%2520string,%2520autoHideAfter?:%2520number);error(message:%2520string,%2520autoHideAfter?:%2520number);error(message:%2520string,%2520param1?:%2520(string%7Cnumber),%2520param2?:%2520number)%2520{var%2520autoHideAfter:%2520number,title:%2520string;//%2520example%2520of%2520mapping%2520the%2520parametersif%2520(param2%2520!=%2520null)%2520{%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520autoHideAfter%2520=%2520param2;%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520title%2520=%2520%253Cstring%253E%2520param1;%2520%2520%2520%2520%2520%2520%2520%2520}%2520%2520%2520%2520%2520%2520%2520%2520else%2520if%2520(param1%2520!=%2520null)%2520{%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520%2520if%2520(typeof%2520param1%2520===^0|0|0|0|0|7|K|S|5|0|0|0|1|0|0|0|0|A|1|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1D|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1E|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1F|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1G|8|@$M|1H|N|1I|O|P]|$M|1J|N|1K|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1L|8|@]|9|@]|A|$]]|$1|S|3|T|5|U|7|1M|8|@]|9|@$M|1N|N|1O|1|1P]]|A|$]]|$1|V|3|R|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1R|8|@]|9|@$M|1S|N|1T|1|1U]]|A|$]]|$1|Y|3|-4|5|6|7|1V|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15|16|-4]]|17|$5|18|12|19|A|$1A|1B]]]]

You can specify multiple method signatures on the interface then have multiple method overloads on the class method:

<pre><code>interface INotificationService {
 error(message: string, title?: string, autoHideAfter?: number);
 error(message: string, autoHideAfter: number);
}

class MyNotificationService implements INotificationService {
 error(message: string, title?: string, autoHideAfter?: number);
 error(message: string, autoHideAfter?: number);
 error(message: string, param1?: (string|number), param2?: number) {
 var autoHideAfter: number,
 title: string;

 // example of mapping the parameters
 if (param2 != null) {
 autoHideAfter = param2;
 title = &lt;string&gt; param1;
 }
 else if (param1 != null) {
 if (typeof param1 === "string") {
 title = param1;
 }
 else {
 autoHideAfter = param1;
 }
 }

 // use message, autoHideAfter, and title here
 }
}
</code></pre>

Now all these will work:

<pre><code>var service: INotificationService = new MyNotificationService();
service.error("My message");
service.error("My message", 1000);
service.error("My message", "My title");
service.error("My message", "My title", 1000);
</code></pre>

...and the <code>error</code> method of <code>INotificationService</code> will have the following options:

<img src="https://i.stack.imgur.com/SdOxQ.png" alt="Overload intellisense">

<a href="http://www.typescriptlang.org/Playground/#src=interface%20INotificationService%20%7B%0D%0A%20%20%20%20error(message%3A%20string%2C%20title%3F%3A%20string%2C%20autoHideAfter%3F%3A%20number)%3B%0D%0A%09error(message%3A%20string%2C%20autoHideAfter%3A%20number)%3B%0D%0A%7D%0D%0A%0D%0Aclass%20MyNotificationService%20implements%20INotificationService%20%7B%0D%0A%20%20%20%20error(message%3A%20string%2C%20title%3F%3A%20string%2C%20autoHideAfter%3F%3A%20number)%3B%0D%0A%09error(message%3A%20string%2C%20autoHideAfter%3F%3A%20number)%3B%0D%0A%09error(message%3A%20string%2C%20param1%3F%3A%20(string%7Cnumber)%2C%20param2%3F%3A%20number)%20%7B%0D%0A%09%09var%20autoHideAfter%3A%20number%2C%0D%0A%09%09%09title%3A%20string%3B%0D%0A%09%09%0D%0A%09%09%2F%2F%20example%20of%20mapping%20the%20parameters%0D%0A%09%09if%20(param2%20!%3D%20null)%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20autoHideAfter%20%3D%20param2%3B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20title%20%3D%20%3Cstring%3E%20param1%3B%0D%0A%20%20%20%20%20%20%20%20%7D%0D%0A%20%20%20%20%20%20%20%20else%20if%20(param1%20!%3D%20null)%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20if%20(typeof%20param1%20%3D%3D%3D%20%22string%22)%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20title%20%3D%20param1%3B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20%7D%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20else%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20autoHideAfter%20%3D%20param1%3B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20%7D%0D%0A%20%20%20%20%20%20%20%20%7D%0D%0A%09%09%0D%0A%09%09console.log(message%2C%20title%2C%20autoHideAfter)%3B%0D%0A%09%7D%0D%0A%7D%0D%0A%0D%0Avar%20service%20%3D%20new%20MyNotificationService()%3B%0D%0Aservice.error(%22My%20message%22)%3B%0D%0Aservice.error(%22My%20message%22%2C%201000)%3B%0D%0Aservice.error(%22My%20message%22%2C%20%22My%20title%22)%3B%0D%0Aservice.error(%22My%20message%22%2C%20%22My%20title%22%2C%201000)%3B" rel="nofollow noreferrer">Playground</a>

blocks|key|132945|text|可以创建一个帮助器方法，该方法根据错误参数接受一个对象参数|type|unstyled|depth|inlineStyleRanges|entityRanges|data|132946|+error(message:+string,+title?:+string,+autoHideAfter?:+number){}

+getError(args:+{+message:+string,+title?:+string,+autoHideAfter?:+number+})+{
++++return+error(args.message,+args.title,+args.autoHideAfter);
+}|code-block|syntax|javascript|132947|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can create a helper method that accept a one object parameter base on error arguments

<pre><code> error(message: string, title?: string, autoHideAfter?: number){}

 getError(args: { message: string, title?: string, autoHideAfter?: number }) {
 return error(args.message, args.title, args.autoHideAfter);
 }
</code></pre>

blocks|key|2698317|text|在TS中，您还可以将参数设置为对象，并将对象的值设置为可选的，这样您就不必定义每个参数，只需定义您想要使用的参数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2698318|​|2698319|public+functionBeingCalled(obj:+{status?:+number,+error?:+string,+message?:+string})+{
++if(obj.message)+{+console.log(obj.message)+}
}

this.functionBeingCalled({message:+'Error+Detected'})|code-block|syntax|javascript|2698320|2698321|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

In TS you could also make your parameters into an Object and make the value of the object optional, that way you don't have to define every parameters, just the one you want to use.
<div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-html lang-html prettyprint-override"><code>public functionBeingCalled(obj: {status?: number, error?: string, message?: string}) {
 if(obj.message) { console.log(obj.message) }
}

this.functionBeingCalled({message: 'Error Detected'})</code></pre>
</div>
</div>

blocks|key|2910349|text|在这种情况下，您可以为那些您不想覆盖的可选参数使用"undefined“值|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2910350|export+interface+INotificationService+{
++++error(message:+string,+title?:+string,+autoHideAfter?:+number);
}|code-block|syntax|javascript|2910351|你可以像这样调用错误方法|2910352|error("it+works",+undefined,+20);|2910353|请注意，null在这里不起作用。|offset|length|style|CODE|2910354|entityMap^0|0|0|0|0|4|4|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

In such cases you can use &quot;undefined&quot; value for those optional params which you do not want to overwrite
<pre><code>export interface INotificationService {
 error(message: string, title?: string, autoHideAfter?: number);
}
</code></pre>
You can call error method like
<pre><code>error(&quot;it works&quot;, undefined, 20);
</code></pre>
Be careful <code>null</code> doesn't work here.

blocks|key|2698354|text|https://www.typescriptlang.org/docs/handbook/functions.html|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2698355|在JavaScript中，每个参数都是可选的，用户可以在他们认为合适的时候不使用它们。当他们这样做时，他们的价值是未定义的。我们可以在TypeScript中添加一个？在参数的末尾，我们希望它是可选的。例如，假设我们希望上面的姓氏参数是可选的：|2698356|function+buildName(firstName:+string,+lastName?:+string)+{
++if+(lastName)+return+firstName+%2B+"+"+%2B+lastName;
++else+return+firstName;
}
+
let+result1+=+buildName("Bob");+//+works+correctly+now
let+result2+=+buildName("Bob",+"Adams",+"Sr.");+//+error,+too+many+parameters
Expected+1-2+arguments,+but+got+3.
let+result3+=+buildName("Bob",+"Adams");+//+ah,+just+right|code-block|syntax|javascript|2698357|entityMap|0|LINK|mutability|MUTABLE|url^0|0|1N|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|W|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|4]]]]

<a href="https://www.typescriptlang.org/docs/handbook/functions.html" rel="nofollow noreferrer">https://www.typescriptlang.org/docs/handbook/functions.html</a>
In JavaScript, every parameter is optional, and users may leave them off as they see fit. When they do, their value is undefined. We can get this functionality in TypeScript by adding a ? to the end of parameters we want to be optional. For example, let’s say we want the last name parameter from above to be optional:
<pre><code>function buildName(firstName: string, lastName?: string) {
 if (lastName) return firstName + &quot; &quot; + lastName;
 else return firstName;
}
 
let result1 = buildName(&quot;Bob&quot;); // works correctly now
let result2 = buildName(&quot;Bob&quot;, &quot;Adams&quot;, &quot;Sr.&quot;); // error, too many parameters
Expected 1-2 arguments, but got 3.
let result3 = buildName(&quot;Bob&quot;, &quot;Adams&quot;); // ah, just right
</code></pre>

blocks|key|2910275|text|您可以尝试将title设置为null。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2910276|这对我很有效。|2910277|error('This+is+the+',null,1000)|code-block|syntax|javascript|2910278|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You could try to set title to null.

This worked for me.

<pre><code>error('This is the ',null,1000)
</code></pre>

blocks|key|2910259|text|您可以在没有接口的情况下做到这一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2910260|class+myClass{
++public+error(message:+string,+title?:+string,+autoHideAfter?+:+number){
++++//....
++}
}|code-block|syntax|javascript|2910261|使用?运算符作为可选参数。|offset|length|style|CODE|2910262|entityMap^0|0|0|2|1|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

You can do this without an interface.

<pre><code>class myClass{
 public error(message: string, title?: string, autoHideAfter? : number){
 //....
 }
}
</code></pre>

use the <code>?</code> operator as an optional parameter.

Given the following signature:

<pre><code>export interface INotificationService {
 error(message: string, title?: string, autoHideAfter?: number);
}
</code></pre>

How can I call the function <code>error()</code> not specifying the <code>title</code> parameter, but setting <code>autoHideAfter</code> to say <code>1000</code>?

How to pass optional parameters while omitting some other optional parameters?

TypeScript

Python

给出以下签名：export interface INotificationService {    error(message: string, title?: string, autoHideAfter?: number);}如果不指定title参数，但将autoHideAfter设置为1000，如何调用函数error()

问如何在传递可选参数的同时省略其他一些可选参数？
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问如何在传递可选参数的同时省略其他一些可选参数？EN

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问如何在传递可选参数的同时省略其他一些可选参数？
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