如何在ES6类的回调函数中访问`self`？

Question

我查看了有关在Javascript中使用self的几个问题，我不相信其中任何一个都能回答我的问题-具体来说就是如何在ES6中创建self class（不是ES5，并且不能在Angular中使用）。

我正在尝试在ES6类的回调函数中使用self。我使用的唯一框架是jQuery。我知道我需要使用self，但是我不知道如何在ES6类中创建self变量。

<!-- BEGIN HTML -->
<div id="Header">
    I want header-message.html to render here...
</div>
<div id="Footer">
    I want footer-message.html to render here...
    (But currently, both HTML chunks will appear here)
</div>
<script src="call/to/jquery.js"></script>     
<script type="module" src="main.js"></script>
<!-- END HTML -->

// BEGIN main.js
import {ContentAsServiceClass} from './contentAsAService.js';
$(function() {    
    $('<div id="HeaderContent"></div>').appendTo('#Header');
    let headerContent = new ContentAsServiceClass(        
        {                
            $htmlTargEl: $('#HeaderContent'),
            htmlFileName: 'header-message.content.html'
        }        
    );
    headerContent.renderContent();

    $('<div id="FooterContent"></div>').appendTo('#Footer');
    let footerContent = new ContentAsServiceClass(        
        {                
            $htmlTargEl: $('#FooterContent'),
            htmlFileName: 'footer-message.content.html'
        }        
    );
    footerContent.renderContent();
});
// END main.js

// BEGIN contentAsAService.js
export let ContentAsServiceClass = class {
constructor(
    {
        // defaults:
        $htmlTargEl =  null,
        htmlFileName = ''
    } = {
        // override defaults:
        $htmlTargEl: $htmlTargEl,
        htmlFileName: htmlFileName      
    }
) {       
    // assign values to instance of object: 
    this.$htmlTargEl = $htmlTargEl,
    this.htmlFileName = htmlFileName;  
    self = this; 
    // assigns `self` to `window` object - which I DON'T want, 
    // and will not work here! But how do I assign `this` to `self` in an ES6 class?
    // Assigning to `var` (`var self = this`) does not work here.
} 
appendHtmlContent(response) {
    // I know I need to use `self` here.
    if(!response || typeof response !== 'string') {
        return false;
    }
    $(self.$htmlTargEl).append(response);
}
getHtmlContent() {   
    $.get(
        'http://localhost/content/my-bucket/' + this.htmlFileName
    ).then(
        this.appendHtmlContent
    );
}
renderContent() {
    this.getHtmlContent();
    }
}

export default ContentAsServiceClass;
// END contentAsAService.js