Uncaught TypeError: Cannot read properties of undefined (reading 'getBody()')

CKEditor Ver.4 This is a cshtml file.

I try to get two kind of content types (with html tags & without one). But it seems not work that.

Error Msg:
Uncaught TypeError: Cannot read properties of undefined (reading 'getBody')

• HTML code:

<textarea class="edit-normal" id="content" msg="content" disabled="disabled">@Html.Raw(Model.Data.Content)</textarea>

• JS code

function GetData() {
    // TODO: Get content with html tags ✓
    var contentEditor = CKEDITOR.replace('content');
    var content = contentEditor.getData();

    // TODO: Get content without html tags
    var rawContent = contentEditor.document.getBody().getText();
}