A React class component that loads a runtime library on componentDidMount(), but only once for multiple instances.

RuntimeSingletonComponent.jsx

import React, { Component } from 'react';

// A "global" promise for the runtime library.
const runtimePromise;

export default RuntimeSingletonComponent extends Component {
  componentDidMount() {
    // Have we previously loaded the runtime library?
    if (!runtimePromise) {
      // import() the runtime library for the first time.
      runtimePromise = import('runtime-lib').then(runtime => runtime);
    }
    
    // Use runtimePromise.then() to do something with the runtime library once it's loaded.
    // Below: this is an imaginary runtime library which works with DOM elements, so we've
    // passed it a reference to the root-level <div> from our render() method.
    runtimePromise.then(runtime => {
      runtime.init(this.root);
    });
  }
  
  componentWillUnmount() {
    // Use runtimePromise.then() once again to work with the runtime library.
    runtimePromise.then(runtime => {
      runtime.destroy(this.root);
    });
  }
  
  render() {
    return <div ref={e => { this.root = e; }} />;
  }
}

Question about line 11: I think that could be simplified to:

runtimePromise = import('runtime-lib');

Yes or no? (Namely, is the identity function redundant?)

Another question: for a runtime library that is used across multiple class components, would it be appropriate to use window.nameOfRuntimeLibraryPromise? Is there a better approach in general?

Also, I'd have to try it of course, but would it be appropriate or better, for that matter, to use a static class property (e.g. RuntimeSingletonComponent.runtimePromise) instead of the module-local const runtimePromise?