workers | References | ArcGIS Maps SDK for JavaScript

import { open } from "@arcgis/core/core/workers.js";

const { open } = await $arcgis.import("@arcgis/core/core/workers.js");

Since: ArcGIS Maps SDK for JavaScript 4.2

This module is a utility framework that simplifies the use of Web Workers in the ArcGIS Maps SDK for JavaScript.

The workers framework takes advantage of multi-core CPUs to perform computationally expensive tasks in a background thread without interfering with the user interface. This framework loads a script and provides a calling function in the main thread using the Connection class. The Connection can then be used to offload jobs asynchronously from the main thread to workers. The workers framework returns a Promise once the job is completed.

Known Limitations

Workers do not have access to document, window and parent objects, and cannot directly affect the parent page; this includes DOM manipulation.

The esriRequest module can be used within worker script with the following exceptions:

esriRequest.options.body FormData value is not supported.
esriRequest.options.responseType supported values are: array-buffer, blob, json, native, text
esriRequest.getHeader is not supported.

See also

ES modules custom workers sample

Type definitions

OpenStrategy

Type definition

Indicates how to load the module. See the table below for a list of possible values.

Possible Value	Description
distributed	The module is loaded in each available worker. Each call to Connection.invoke() will be targeting an available worker. Use this strategy if the module doesn't maintain information between invocations (stateless).
dedicated	The module is loaded in one worker. Each call to Connection.invoke() will be targeting a same worker. Use this strategy if the module maintains information from previous invocations or communication between main and worker threads needs to be stateful.
local	The module is loaded in the main thread. Use this strategy when using the worker framework API while disabling the use of workers.

Type: "distributed" | "dedicated" | "local"

OpenOptions

Type definition

Supertypes: AbortOptions

client

Property

Type: any | undefined

The objects defining the API accessible from the module.

strategy

Property

Type: OpenStrategy | undefined

Indicates how to load the module. See the table below for a list of possible values.

Default value: distributed

Functions

open

Function

Opens a connection to workers and loads a script with the workers framework.

See also

Connection

Signature: open (modulePath: string, options?: OpenOptions): Promise<Connection>

Parameters

Parameter	Type	Description	Required
modulePath	string	A fully qualified URL to a script to execute with the workers framework.
options	OpenOptions	Worker options. See properties below for object specifications.

Returns: Promise<Connection>
Resolves to an instance of Connection.

Examples

// Set the path for the worker's AMD loader configuration
// to a folder called workersFolder.
esriConfig.workers.loaderConfig = {
 paths: {
   myWorkers: new URL("./workersFolder", document.baseURI).href
 }
};

// load myWorkers/Calculator.js in the workers framework
// and invoke its "getMaxNumber" method
workers.open("myWorkers/Calculator")
  .then((connection) => {
    return connection.invoke("getMaxNumber", [0, 1, 2, 3, 4]);
  })
  .then((result) => {
    console.log(result);
  });

//*********************************************************
// module: workerFolder/Calculator.js
//*********************************************************
define([], () => {
  return {
    // this function can be invoked from the main thread
    getMaxNumber: function (number) {
      return Math.max.apply(null, numbers);
    }
  };
});

// Load workerScripts/TimeOfTheDay.js in the workers framework
// We define an API accessible from the module
workers.open(new URL("./workerScripts/TimeOfDay.js", document.baseURI).href, {
  client: {
    getCurrentTime: function() {
      return Date.now();
    }
  }
})
  .then((connection) => {
    return connection.invoke("timeOfTheDay");
  })
  .then((result) => {
    console.log(result);
  });

//*********************************************************
// module: workerScripts/TimeOfTheDay.js
//*********************************************************

define([], () => {

  return {
    timeOfTheDay: function(noArgs, remoteClient) {
      // call back the main thread to get the current time over there.
      return remoteClient.invoke("getCurrentTime")
        .then((time) => {
          return "The time is " + time;
        });
    }
  };
});