javascript - Relative references must start with either "/", "./", or "../"

Question

I am newbie to lit-element, and when use import to include the library, I am getting error as:

Uncaught TypeError: Failed to resolve module specifier "lit-element". Relative references must start with either "/", "./", or "../".

Please provide any alternatives/solutions.

import { LitElement, html } from 'lit-element';

class MyElement extends LitElement {
  render(){
    return html`
      <div>
        <p>A paragraph</p>
      </div>
    `;
  }
}
customElements.define('my-element', MyElement);

Answer 1

This doesn't work because js imports must reference a specific file with either a relative path or an absolute path, assuming your project structure is something like the following:

/node_modules
  /lit-element
  /other-library
/src
  /components
    my-element.js
index.html

From my-element.js, your import would be

import {LitElement, html} from '../../node_modules/lit-element/lit-element.js'

However, since this kind of configuration is confusing and you'll probably end up setting a build script sometime too, the recommendation would be to keep your imports as they are right now and use a dev server that remaps your imports to node_modules like open-wc's web server

Update (Feb. 2021): The web server mentioned on this question has gone through a few iterations and improvements. The current package is @web/dev-server