对于Textarea - Angular，类型'HTMLElement'上不存在属性'value'

问题描述

使用Angular 4（typescript），我有以下HTML代码：

Using Angular 4 (typescript), I have the below HTML code:

 <div *ngIf="dataService.selected_markers.length == 0" id="tsnPasteContainer">
      <form style="width: 100%; height: 100%">
        <textarea id="tsn_list" style="width: 100%; height: 100%" type="text" name="tsn_list" placeholder="e.g. 2001311,2425302,2153542,2435974"></textarea>
      </form>
    </div>

我正在尝试使用以下内容将用户输入的数据输入textarea：

I am trying to get the data that the user is typing into the textarea using:

public parseTSNs(){
    let tsnString = document.getElementById("tsn_list").value;
    console.log("User inputted string: " + tsnString);
}

此功能由一个按钮调用。

This function is called by a button.

由于以下原因，代码未编译：

The code is not compiling due to:

Property 'value' does not exist on type 'HTMLElement'

这应该是一个简单的函数。我究竟做错了什么？ W3schools从textarea获取值显示'.value'作为必需的函数！

This should be a simple function. What am I doing wrong? W3schools "getting values from textarea" shows '.value' as the required function!

推荐答案

你只需断言该类型您的元素是 HTMLTextAreaElement 。因为 document.getElementById 返回 HTMLElement 而且并非所有html元素都具有值 property：

You just have to assert that the type of your element is HTMLTextAreaElement. Because document.getElementById returns HTMLElement and not all html elements have the value property:

let tsnString = (document.getElementById("tsn_list") as HTMLTextAreaElement).value;

但是当您使用Angular时，您可能应该使用数据绑定而不是自己查询值

But seeing as you use Angular, you should probably be using data binding instead of querying the values yourself

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