How to dynamically import a module in lwc

Could you please try

export Calculator {
    static add = (a, b) =>  a + b;
}

without the default/class keyword. Worked for me.

You can create a LWC only with the XML by default and the JS.

In the JS you export what you want, for example:

export function getQueryParameters() {
...
}
export function whateverFunction(){
...
}

this LWC is called jsUtilities, and the code only has this functions.

Then, when you want to import, you have to use the syntax like this:

import { getQueryParameters, whateverFunction } from 'c/jsUtilities';

And to use it just don't use this.getQueryParameters() but just the name of the function:

renderedCallback(){
        if(!this.initialized){
            let urlParams = getQueryParameters();
...

Do you have below in the meta.xml file for the LWC?

<capabilities>
    <capability>lightning__dynamicComponent</capability>
</capabilities>

Also, here is some sample code you can reference for dynamic components.

import { LightningElement, api } from "lwc";
import { ShowToastEvent } from "lightning/platformShowToastEvent";
import { reduceErrors } from "c/ldsUtils";
const VIEW_MAPPING = {
    card: () => import("c/accountContactsCardView"),
    table: () => import("c/accountContactsTableView")
};
export default class AccountContacts extends LightningElement {
    // Public properties
    @api recordId;
    /** Component constructor that allows for importing the dynamic component */
    componentConstructor;
    /** The default component view */
    view = "card";
    // Private properties
    _isLoading;

    get viewOptions() {
        return [
            { label: "Card", value: "card" },
            { label: "Table", value: "table" }
        ];
    }

    get isLoading() {
        return this._isLoading;
    }

    /**
    * Imports the default component
    */
    async connectedCallback() {
        this._isLoading = true;
        try {
            const { default: ctor } = await import("c/accountContactsCardView");
            this.componentConstructor = ctor;
        } catch (error) {
            this.dispatchEvent(
                new ShowToastEvent({
                    title: "Component Load Error",
                    message: reduceErrors(error).join(", "),
                    variant: "error",
                    mode: "pester",
                })
            );
        } finally {
            this._isLoading = false;
        }
    }

    /**
    * Sets the view which determines what component to display
    * @param {Object} event the change event
    */
    handleChange(event) {
        this._isLoading = true;
        this.view = event.detail.value;
        VIEW_MAPPING[this.view]().then(({ default: ctor }) => {
            this.componentConstructor = ctor;
        }).catch((error) => {
            this.dispatchEvent(
                new ShowToastEvent({
                    title: "Component Load Error",
                    message: reduceErrors(error).join(", "),
                    variant: "error",
                    mode: "pester",
                })
            );
        }).finally(() => {
            this._isLoading = false;
        });
    }
}

Template

<template>
    <div class="slds-m-around_medium">
        <lightning-card title="Contacts" icon-name="standard:contact">
            <lightning-combobox
                name="contactsView"
                label="Contacts View"
                value={view}
                placeholder="Select Contacts View"
                options={viewOptions}
                onchange={handleChange}
            ></lightning-combobox>
        </lightning-card>
    </div>
    <div lwc:if={isLoading} class="slds-is-relative">
        <lightning-spinner alternative-text="Loading..." variant="brand"> </lightning-spinner>
    </div>
    <lwc:component
        ref="contactsView"
        record-id={recordId}
        lwc:is={componentConstructor}
    ></lwc:component>
</template>