workers

AMD: require(["esri/core/workers"], (workers) => { /* code goes here */ });
ESM: import * as workers from "@arcgis/core/core/workers";
Object: esri/core/workers
Since: ArcGIS API for JavaScript 4.2

This module is a utility framework that simplifies the use of Web Workers in the ArcGIS API 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

Method Overview

Name Return Type Summary Object
Promise<Connection>more details

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

more detailsworkers

Method Details

open(modulePath, options){Promise<Connection>}static

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

Parameters:
Specification:
modulePath String

A fully qualified URL to a script to execute with the workers framework.

options Object
optional

Worker options. See properties below for object specifications.

Specification:
client Object
optional

The objects defining the API accessible from the module.

strategy String
optional
Default Value: distributed

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 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 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.

Possible Values:"distributed"|"dedicated"|"local"

signal AbortSignal
optional

AbortSignal allows for cancelable asynchronous job. If canceled, the promise will be rejected with an error named AbortError. See also AbortController.

Returns:
Type Description
Promise<Connection> Resolves to an instance of Connection.
See also:
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(this, "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("workerScripts/TimeOfTheDay", {
  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;
        });
    }
  };
});

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