scrap - simple web component test - async method

simple-test.html

<script>
  (function(window, document, undefined) {
    
    const thisDoc = document.currentScript.ownerDocument;
    
    class TestComponent extends HTMLElement {
      
      constructor() {
        super();
        this.attachShadow({mode: 'open'});
        this.shadowRoot.innerHTML = "<h1>Simple Test WebComponent</h1>";
      }
      
      async getImageWidthByUrl(url, method) {
        
        let imgEl;
        if(method === "new Image()") {
          
          imgEl = new Image();
          
        } else if(method === "document.createElement") {
          
          imgEl = document.createElement("img");
          
        } else if(method === "document.currentScript.ownerDocument.createElement") {
          
          imgEl = thisDoc.createElement("img"); 
          
        }
        
        let imgLoad = new Promise((resolve, reject) => {
          imgEl.onload = resolve;
          imgEl.onerror = reject;
        });
        imgEl.src = url;
        await imgLoad;
        
        return imgEl.naturalWidth;
        
      }
      
    }
    window.customElements.define('test-component', TestComponent);
  })(window, document);
</script>