阿玛说必须不用有网名 發表於 2020-7-21 19:31:00

TypeScript 中的':' 和'?:'的区别

<div>在rect中, 有下面的代码:&nbsp;</div>
<div>&nbsp;</div>
<div>export&nbsp;type&nbsp;ReactComponentLike&nbsp;=</div>
<div>&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;string</div>
<div>&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;((props:&nbsp;any,&nbsp;context?:&nbsp;any)&nbsp;=&gt;&nbsp;any)</div>
<div>&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;(new&nbsp;(props:&nbsp;any,&nbsp;context?:&nbsp;any)&nbsp;=&gt;&nbsp;any);</div>
<div>&nbsp;</div>
<div>props: any, 使用的是:&nbsp;</div>
<div>context?:any , 却使用的是?:&nbsp;</div>
<div>&nbsp;</div>
<div>这两个符号有什么区别呢?</div>
<div>&nbsp;</div>
<div><span style="background-color: rgba(255, 102, 0, 1)">:这两个都表示参数的类型, 不同的是, 一个参数构造函数必须有的, 而另外一个, 是可选的.</span></div>
<div>&nbsp;</div>
<div>看一下下面的代码:</div>
<div>&nbsp;</div>
<div>//sharp.ts</div>
<div>
<p>interface Shape {<br>    name: string;<br>    width: number;<br>    height: number;<br>    color?: string;<br>}<br> <br>function area(shape : Shape) {<br>    var area = shape.width * shape.height;<br>    return "I'm " + shape.name + " with area " + area + " cm squared";<br>}<br> <br>console.log( area( {name: "rectangle", width: 30, height: 15} ) );<br>console.log( area( {name: "square", width: 30, height: 30, color: "blue"} ) );</p>
<p>&nbsp;</p>
</div><br><br>
来源：https://www.cnblogs.com/montai/p/13356990.html
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