Rails Stimulus add plugin to Leaflet not yarn building - ruby-on-rails

Question

Worked through how to get Leaflet in Stimulus and a Leaflet plugin leaflet.control.opacity to load, but the plugin loads with an error.
[watch] build started (change: "app/javascript/controllers/control_opacity_controller.js")
✘ [ERROR] Cannot assign to "i" because it is a constant
node_modules/leaflet.control.opacity/dist/L.Control.Opacity.js:1:2656:
1 │ ...ue=100*t.layer.options.opacity):i=this._createRadioElement("leaf...
╵ ^
The symbol "i" was declared a constant here:
node_modules/leaflet.control.opacity/dist/L.Control.Opacity.js:1:2498:
1 │ ...document.createElement("label"),i=document.createElement("input"...
The plugin works in other contexts, but not here. The Stimulus controller
// app/javascript/controllers/control_opacity_controller.js
import { Controller } from "#hotwired/stimulus"
import L from "leaflet"
import Opacity from "leaflet.control.opacity"
export default class extends Controller {
static targets = [ "map" ]
connect() {
const m_color = new L.tileLayer('https://tile.mierune.co.jp/mierune/{z}/{x}/{y}.png', {
attribution:
"Maptiles by <a href='http://mierune.co.jp/' target='_blank'>MIERUNE</a>, under CC BY. Data by <a href='http://osm.org/copyright' target='_blank'>OpenStreetMap</a> contributors, under ODbL.",
});
const m_mono = new L.tileLayer('https://tile.mierune.co.jp/mierune_mono/{z}/{x}/{y}.png', {
attribution:
"Maptiles by <a href='http://mierune.co.jp/' target='_blank'>MIERUNE</a>, under CC BY. Data by <a href='http://osm.org/copyright' target='_blank'>OpenStreetMap</a> contributors, under ODbL.",
});
const o_std = new L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
attribution: '© OpenStreetMap contributors',
});
const t_pale = new L.tileLayer('https://cyberjapandata.gsi.go.jp/xyz/pale/{z}/{x}/{y}.png', {
attribution:
"<a href='http://www.gsi.go.jp/kikakuchousei/kikakuchousei40182.html' target='_blank'>国土地理院</a>",
});
const t_ort = new L.tileLayer('https://cyberjapandata.gsi.go.jp/xyz/ort/{z}/{x}/{y}.jpg', {
attribution:
"<a href='http://www.gsi.go.jp/kikakuchousei/kikakuchousei40182.html' target='_blank'>国土地理院</a>",
});
const map = L.map('maplco', {
center: [35.6831925, 139.7511307],
zoom: 13,
zoomControl: true,
layers: [m_mono],
});
//BaseLayer
const Map_BaseLayer = {
'MIERUNE Color': m_color,
'MIERUNE MONO': m_mono,
};
//AddLayer
const Map_AddLayer = {
'OSM': o_std,
'GSI Pale': t_pale,
'GSI Ort': t_ort,
};
//LayerControl
L.control
.layers(Map_BaseLayer, Map_AddLayer, {
collapsed: false,
})
.addTo(map);
//OpacityControl
L.control
.opacity(Map_AddLayer, {
label: 'Layers Opacity',
})
.addTo(map);
}
}