esri-loader

A tiny library to help load ArcGIS API for JavaScript modules in non-Dojo applications.

Install

npm install esri-loader

Usage

The code below shows how you can load the ArcGIS API for JavaScript and then create a map. Where you place this code in your application will depend on what framework you are using. See below for example applications.

Loading Styles

Before you can use the ArcGIS API in your app, you'll need to load the styles, for example:

/* esri styles */
@import url('https://js.arcgis.com/3.20/esri/css/esri.css');

Pre-loading the ArcGIS API for JavaScript

If you have good reason to believe that the user is going to transition to a map route, you may want to start pre-loading the ArcGIS API as soon as possible w/o blocking rendering, for example:

import * as esriLoader from 'esri-loader';

// preload the ArcGIS API
esriLoader.bootstrap((err) => {
  if (err) {
    // handle any loading errors
    console.error(err);
  } else {
    // optionall execute any code once it's preloaded
  }
}, {
  // use a specific version instead of latest 4.x
  url: '//js.arcgis.com/3.20/';
});

Lazy Loading the ArcGIS API for JavaScript

Alternatively, if users may never end up visiting any map routes, you can lazy load the ArcGIS API for JavaScript the first time a user visits a route with a map, for example:

// import the esri-loader library
import * as esriLoader from 'esri-loader';

// has the ArcGIS API been added to the page?
if (!esriLoader.isLoaded()) {
  // no, lazy load it the ArcGIS API before using its classes
  esriLoader.bootstrap((err) => {
    if (err) {
      console.error(err);
    } else {
      // once it's loaded, create the map
      createMap();
    }
  }, {
    // use a specific version instead of latest 4.x
    url: 'https://js.arcgis.com/3.20/'
  });
} else {
  // ArcGIS API is already loaded, just create the map
  createMap();
}

Loading Modules from the ArcGIS API for JavaScript

Once you've loaded the API using one of the above methods, you can then load modules. Here's an example of how you could load and use the 3.x Map and VectorTileLayer classes in a component to create a map:

// create a map on the page
function createMap() {
  // first, we use Dojo's loader to require the map class
  esriLoader.dojoRequire(['esri/map'], (Map) => {
    // create map with the given options at a DOM node w/ id 'mapNode' 
    let map = new Map('mapNode', {
      center: [-118, 34.5],
      zoom: 8,
      basemap: 'dark-gray'
    });
  });
}

Why is this needed?

This blog post explains how libraries like this provide a workaround to the challenges of loading ArcGIS API for JavaScript modules from bundlers like webpack.

Examples

Here are some applications that use this library:

Angular

• angular2-esri-loader - An Angular 2 service that wraps this library to make it easy to bring it into any Angular 2 application
• angular2-esri4-components - A set of Angular 2 components to work with ArcGIS API for JavaScript v4.x

React

• esri-react-router-example - An example reaact-router application that uses this library to preload the ArcGIS API
• create-react-app-esri-loader - An example create-react-app application that uses this library to load the ArcGIS API

Vue

• City of Baltimore: Map Gallery - Map Gallery built with Vue.js that uses this library to load the ArcGIS API