如何在 TypeScript 中断言 HTMLElement 的类型? [英] How to assert a type of an HTMLElement in TypeScript?

问题描述

我正在尝试这样做:

var script:HTMLScriptElement = document.getElementsByName("script")[0];
alert(script.type);

但它给了我一个错误:

Cannot convert 'Node' to 'HTMLScriptElement': Type 'Node' is missing property 'defer' from type 'HTMLScriptElement'
(elementName: string) => NodeList

除非我将其强制转换为正确的类型，否则我无法访问脚本元素的类型"成员，但我不知道如何执行此操作.我搜索了文档 &样品，但我找不到任何东西.

I can't access the 'type' member of the script element unless I cast it to the correct type, but I don't know how to do this. I searched the docs & samples, but I couldn't find anything.

推荐答案

TypeScript 使用 '<>' 来包围强制转换，所以上面变成了:

TypeScript uses '<>' to surround casts, so the above becomes:

var script = <HTMLScriptElement>document.getElementsByName("script")[0];

但是，不幸的是你不能这样做:

However, unfortunately you cannot do:

var script = (<HTMLScriptElement[]>document.getElementsByName(id))[0];

你得到错误

Cannot convert 'NodeList' to 'HTMLScriptElement[]'

但是你可以这样做:

(<HTMLScriptElement[]><any>document.getElementsByName(id))[0];

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