messages_javascript.html
1 <!DOCTYPE html> 2 <html lang="en" dir="ltr"> 3 <head prefix="og: http://ogp.me/ns#"> 4 <meta charset="utf-8"> 5 <title>Messages in JavaScript | Embark</title> 6 <meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1"> 7 <meta name="viewport" content="width=device-width, initial-scale=1"> 8 <!-- Canonical links --> 9 <link rel="canonical" href="https://framework.embarklabs.io/docs/messages_javascript.html"> 10 <!-- Alternative links --> 11 12 13 <!-- Icon --> 14 <meta name="msapplication-TileColor" content="#080E1A"> 15 <link rel="icon" type="image/png" href="/assets/images/favicon-16.png" sizes="16x16" /> 16 <link rel="icon" type="image/png" href="/assets/images/favicon-32.png" sizes="32x32" /> 17 18 <link rel="apple-touch-icon" sizes="76x76" href="/assets/images/apple-touch-icon-60x60-precomposed.png"> 19 <link rel="apple-touch-icon" sizes="76x76" href="/assets/images/apple-touch-icon-76x76-precomposed.png"> 20 <link rel="apple-touch-icon" sizes="120x120" href="/assets/images/apple-touch-icon-120x120-precomposed.png"> 21 <link rel="apple-touch-icon" sizes="152x152" href="/assets/images/apple-touch-icon-152x152-precomposed.png"> 22 <link rel="apple-touch-icon" sizes="180x180" href="/assets/images/apple-touch-icon-precomposed.png"> 23 <link rel="apple-touch-icon" href="/assets/images/apple-touch-icon-precomposed.png"> 24 <!-- CSS --> 25 26 <link rel="stylesheet" href="/css/embark.css"> 27 28 <!-- endbuild --> 29 30 <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.min.css"> 31 <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.css" /> 32 33 <!-- RSS --> 34 <link rel="alternate" href="/atom.xml" title="Embark"> 35 <meta property="og:image" content="/img/share.png?v=0.0.5" /> 36 <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.15.4/styles/dracula.min.css"> 37 38 <script async defer src="https://buttons.github.io/buttons.js"></script> 39 40 41 <script> 42 !function(root, factory) { 43 "function" == typeof define && define.amd ? // AMD. 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Embark?</a> 350 </li> 351 </ul> 352 </div> --> 353 </li> 354 355 <li class="o-list-bare__item"> 356 <a href="/docs/configuration.html" title="Configuration" class="u-link-uniform ">Configuration</a> 357 <!-- <div class="o-distance-m"> 358 <ul class="o-list-bare c-navigation__subnav"> 359 <li class="o-list-bare__item"> 360 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 361 </li> 362 </ul> 363 </div> --> 364 </li> 365 366 <li class="o-list-bare__item"> 367 <a href="/docs/pipeline_and_webpack.html" title="Building & Compiling" class="u-link-uniform ">Building & Compiling</a> 368 <!-- <div class="o-distance-m"> 369 <ul class="o-list-bare c-navigation__subnav"> 370 <li class="o-list-bare__item"> 371 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 372 </li> 373 </ul> 374 </div> --> 375 </li> 376 377 <li class="o-list-bare__item"> 378 <a href="/docs/executing_scripts.html" title="Executing Scripts" class="u-link-uniform 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class="o-distance-m"> 409 <ul class="o-list-bare c-navigation__subnav"> 410 <li class="o-list-bare__item"> 411 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 412 </li> 413 </ul> 414 </div> --> 415 </li> 416 417 <li class="o-list-bare__item"> 418 <a href="/docs/contracts_deployment.html" title="Accounts & Deployment" class="u-link-uniform ">Accounts & Deployment</a> 419 <!-- <div class="o-distance-m"> 420 <ul class="o-list-bare c-navigation__subnav"> 421 <li class="o-list-bare__item"> 422 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 423 </li> 424 </ul> 425 </div> --> 426 </li> 427 428 <li class="o-list-bare__item"> 429 <a href="/docs/contracts_imports.html" title="Special Imports" class="u-link-uniform ">Special Imports</a> 430 <!-- <div class="o-distance-m"> 431 <ul class="o-list-bare c-navigation__subnav"> 432 <li class="o-list-bare__item"> 433 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 434 </li> 435 </ul> 436 </div> --> 437 </li> 438 439 <li class="o-list-bare__item"> 440 <a href="/docs/contracts_testing.html" title="Testing" class="u-link-uniform ">Testing</a> 441 <!-- <div class="o-distance-m"> 442 <ul class="o-list-bare c-navigation__subnav"> 443 <li class="o-list-bare__item"> 444 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 445 </li> 446 </ul> 447 </div> --> 448 </li> 449 450 <li class="o-list-bare__item"> 451 <a href="/docs/contracts_javascript.html" title="Smart Contracts in JavaScript" class="u-link-uniform ">Smart Contracts in JavaScript</a> 452 <!-- <div class="o-distance-m"> 453 <ul class="o-list-bare c-navigation__subnav"> 454 <li class="o-list-bare__item"> 455 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 456 </li> 457 </ul> 458 </div> --> 459 </li> 460 461 </ul> 462 </div> 463 464 <div class="o-distance-xl"> 465 <h3 class="c-category-title">Blockchain Client</h3> 466 <ul class="o-list-bare"> 467 468 <li class="o-list-bare__item"> 469 <a href="/docs/blockchain_configuration.html" title="Configuration" class="u-link-uniform ">Configuration</a> 470 <!-- <div class="o-distance-m"> 471 <ul class="o-list-bare c-navigation__subnav"> 472 <li class="o-list-bare__item"> 473 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 474 </li> 475 </ul> 476 </div> --> 477 </li> 478 479 <li class="o-list-bare__item"> 480 <a href="/docs/blockchain_accounts_configuration.html" title="Managing Accounts" class="u-link-uniform ">Managing Accounts</a> 481 <!-- <div class="o-distance-m"> 482 <ul class="o-list-bare c-navigation__subnav"> 483 <li class="o-list-bare__item"> 484 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 485 </li> 486 </ul> 487 </div> --> 488 </li> 489 490 </ul> 491 </div> 492 493 <div class="o-distance-xl"> 494 <h3 class="c-category-title">Storage (IPFS/Swarm)</h3> 495 <ul class="o-list-bare"> 496 497 <li class="o-list-bare__item"> 498 <a href="/docs/storage_configuration.html" title="Configuration" class="u-link-uniform ">Configuration</a> 499 <!-- <div class="o-distance-m"> 500 <ul class="o-list-bare c-navigation__subnav"> 501 <li class="o-list-bare__item"> 502 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 503 </li> 504 </ul> 505 </div> --> 506 </li> 507 508 <li class="o-list-bare__item"> 509 <a href="/docs/storage_deployment.html" title="Deploying apps" class="u-link-uniform ">Deploying apps</a> 510 <!-- <div class="o-distance-m"> 511 <ul class="o-list-bare c-navigation__subnav"> 512 <li class="o-list-bare__item"> 513 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 514 </li> 515 </ul> 516 </div> --> 517 </li> 518 519 <li class="o-list-bare__item"> 520 <a href="/docs/storage_javascript.html" title="Storage APIs in JavaScript" class="u-link-uniform ">Storage APIs in JavaScript</a> 521 <!-- <div class="o-distance-m"> 522 <ul class="o-list-bare c-navigation__subnav"> 523 <li class="o-list-bare__item"> 524 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 525 </li> 526 </ul> 527 </div> --> 528 </li> 529 530 </ul> 531 </div> 532 533 <div class="o-distance-xl"> 534 <h3 class="c-category-title">Messages (Whisper)</h3> 535 <ul class="o-list-bare"> 536 537 <li class="o-list-bare__item"> 538 <a href="/docs/messages_configuration.html" title="Configuration" class="u-link-uniform ">Configuration</a> 539 <!-- <div class="o-distance-m"> 540 <ul class="o-list-bare c-navigation__subnav"> 541 <li class="o-list-bare__item"> 542 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 543 </li> 544 </ul> 545 </div> --> 546 </li> 547 548 <li class="o-list-bare__item"> 549 <a href="/docs/messages_javascript.html" title="Messages in JavaScript" class="u-link-uniform is-active">Messages in JavaScript</a> 550 <!-- <div class="o-distance-m"> 551 <ul class="o-list-bare c-navigation__subnav"> 552 <li class="o-list-bare__item"> 553 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 554 </li> 555 </ul> 556 </div> --> 557 </li> 558 559 </ul> 560 </div> 561 562 <div class="o-distance-xl"> 563 <h3 class="c-category-title">Naming Systems (ENS)</h3> 564 <ul class="o-list-bare"> 565 566 <li class="o-list-bare__item"> 567 <a href="/docs/naming_configuration.html" title="Configuration" class="u-link-uniform ">Configuration</a> 568 <!-- <div class="o-distance-m"> 569 <ul class="o-list-bare c-navigation__subnav"> 570 <li class="o-list-bare__item"> 571 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 572 </li> 573 </ul> 574 </div> --> 575 </li> 576 577 <li class="o-list-bare__item"> 578 <a href="/docs/naming_javascript.html" title="Naming Systems in JavaScript" class="u-link-uniform ">Naming Systems in JavaScript</a> 579 <!-- <div class="o-distance-m"> 580 <ul class="o-list-bare c-navigation__subnav"> 581 <li class="o-list-bare__item"> 582 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 583 </li> 584 </ul> 585 </div> --> 586 </li> 587 588 </ul> 589 </div> 590 591 <div class="o-distance-xl"> 592 <h3 class="c-category-title">Plugins</h3> 593 <ul class="o-list-bare"> 594 595 <li class="o-list-bare__item"> 596 <a href="/docs/installing_plugins.html" title="Installing plugins" class="u-link-uniform ">Installing plugins</a> 597 <!-- <div class="o-distance-m"> 598 <ul class="o-list-bare c-navigation__subnav"> 599 <li class="o-list-bare__item"> 600 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 601 </li> 602 </ul> 603 </div> --> 604 </li> 605 606 <li class="o-list-bare__item"> 607 <a href="/docs/creating_plugins.html" title="Creating plugins" class="u-link-uniform ">Creating plugins</a> 608 <!-- <div class="o-distance-m"> 609 <ul class="o-list-bare c-navigation__subnav"> 610 <li class="o-list-bare__item"> 611 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 612 </li> 613 </ul> 614 </div> --> 615 </li> 616 617 <li class="o-list-bare__item"> 618 <a href="/docs/plugin_reference.html" title="Plugin APIs" class="u-link-uniform ">Plugin APIs</a> 619 <!-- <div class="o-distance-m"> 620 <ul class="o-list-bare c-navigation__subnav"> 621 <li class="o-list-bare__item"> 622 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 623 </li> 624 </ul> 625 </div> --> 626 </li> 627 628 </ul> 629 </div> 630 631 <div class="o-distance-xl"> 632 <h3 class="c-category-title">Cockpit Guides</h3> 633 <ul class="o-list-bare"> 634 635 <li class="o-list-bare__item"> 636 <a href="/docs/cockpit_introduction.html" title="Introduction" class="u-link-uniform ">Introduction</a> 637 <!-- <div class="o-distance-m"> 638 <ul class="o-list-bare c-navigation__subnav"> 639 <li class="o-list-bare__item"> 640 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 641 </li> 642 </ul> 643 </div> --> 644 </li> 645 646 <li class="o-list-bare__item"> 647 <a href="/docs/cockpit_dashboard.html" title="Using the Dashboard" class="u-link-uniform ">Using the Dashboard</a> 648 <!-- <div class="o-distance-m"> 649 <ul class="o-list-bare c-navigation__subnav"> 650 <li class="o-list-bare__item"> 651 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 652 </li> 653 </ul> 654 </div> --> 655 </li> 656 657 <li class="o-list-bare__item"> 658 <a href="/docs/cockpit_deployment.html" title="Deployment" class="u-link-uniform ">Deployment</a> 659 <!-- <div class="o-distance-m"> 660 <ul class="o-list-bare c-navigation__subnav"> 661 <li class="o-list-bare__item"> 662 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 663 </li> 664 </ul> 665 </div> --> 666 </li> 667 668 <li class="o-list-bare__item"> 669 <a href="/docs/cockpit_explorer.html" title="Explorer View" class="u-link-uniform ">Explorer View</a> 670 <!-- <div 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</ul> 698 </div> --> 699 </li> 700 701 </ul> 702 </div> 703 704 <div class="o-distance-xl"> 705 <h3 class="c-category-title">Reference</h3> 706 <ul class="o-list-bare"> 707 708 <li class="o-list-bare__item"> 709 <a href="/docs/embark_commands.html" title="CLI Commands" class="u-link-uniform ">CLI Commands</a> 710 <!-- <div class="o-distance-m"> 711 <ul class="o-list-bare c-navigation__subnav"> 712 <li class="o-list-bare__item"> 713 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 714 </li> 715 </ul> 716 </div> --> 717 </li> 718 719 </ul> 720 </div> 721 722 <div class="o-distance-xl"> 723 <h3 class="c-category-title">Miscellaneous</h3> 724 <ul class="o-list-bare"> 725 726 <li class="o-list-bare__item"> 727 <a href="/docs/migrating_from_3.x.html" title="Migrating from Embark 3.x" class="u-link-uniform ">Migrating from Embark 3.x</a> 728 <!-- <div class="o-distance-m"> 729 <ul class="o-list-bare c-navigation__subnav"> 730 <li class="o-list-bare__item"> 731 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 732 </li> 733 </ul> 734 </div> --> 735 </li> 736 737 <li class="o-list-bare__item"> 738 <a href="/docs/troubleshooting.html" title="Troubleshooting" class="u-link-uniform ">Troubleshooting</a> 739 <!-- <div class="o-distance-m"> 740 <ul class="o-list-bare c-navigation__subnav"> 741 <li class="o-list-bare__item"> 742 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 743 </li> 744 </ul> 745 </div> --> 746 </li> 747 748 <li class="o-list-bare__item"> 749 <a href="/docs/contributing.html" title="Contributing" class="u-link-uniform ">Contributing</a> 750 <!-- <div class="o-distance-m"> 751 <ul class="o-list-bare c-navigation__subnav"> 752 <li class="o-list-bare__item"> 753 <a href="#" title="What is Embark?" class="u-link-uniform">What is Embark?</a> 754 </li> 755 </ul> 756 </div> --> 757 </li> 758 759 </ul> 760 </div> 761 762 </nav> 763 </div> 764 </div> 765 <div class="o-guided-content__content"> 766 <p class="c-meta">Last updated: January 19th 2020 767 (<a href="https://github.com/embarklabs/embark/edit/master/site/source/docs/messages_javascript.md" target="_blank"> 768 Improve this guide <svg class="c-icon c-icon--xs"><use xlink:href="/../../assets/icons/symbols.svg#icon-pen-write-paper"></use></svg> 769 </a>) 770 </p> 771 <div class="o-standard-page"> 772 <h1>Messages in JavaScript</h1> 773 <p>Embark’s companion library EmbarkJS comes with some convenient APIs to easily subscribe to and sending messages using messages protocols like Whisper. In this guide we’ll take a closer look how this works.</p> 774 <p>Make sure to read our guide in <a href="/docs/javascript.html">using EmbarkJS</a> first.</p> 775 <h2 id="Setting-up-EmbarkJS"><a href="#Setting-up-EmbarkJS" class="headerlink" title="Setting up EmbarkJS"></a>Setting up EmbarkJS</h2><p>By default Embark will initialize EmbarkJS with the provider configured at <code>config/communication.js</code>. However if we are using EmbarkJS directly or wish to change the provider configuration at runtime, we can do so using the <code>setProvider()</code> method:</p> 776 <figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">EmbarkJS.Messages.setProvider('whisper')</span><br></pre></td></tr></table></figure> 777 778 <h2 id="Listening-to-messages"><a href="#Listening-to-messages" class="headerlink" title="Listening to messages"></a>Listening to messages</h2><p>We can subscribe to channels using the <code>listenTo()</code> method by specifying a list of channel topics like this:</p> 779 <figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">EmbarkJS.Messages.listenTo({</span><br><span class="line"> topic: ['topic1', 'topic2']</span><br><span class="line">}).subscribe(message {</span><br><span class="line"> console.log('received: ' + message);</span><br><span class="line">});</span><br></pre></td></tr></table></figure> 780 781 <p><code>listenTo()</code> returns an Observable that we can subscribe to. Observables work great if multiple values can be emitted over time, which is exactly the case for messages being emitted with Whisper. In other words, this is a long-living Observable, so it’s important to unsubscribe from it once we’re no longer interested in the data. Otherwise we’ll introduce memory leaks.</p> 782 <h2 id="Sending-messages"><a href="#Sending-messages" class="headerlink" title="Sending messages"></a>Sending messages</h2><p>Sending messages can be done using the <code>sendMessage()</code> method and it’s entirely up to use whether we want to send plain text messages or even objects.</p> 783 <p>Here’s how to send a plain text message to the <code>sometopic</code> topic:</p> 784 <figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">EmbarkJS.Messages.sendMessage({</span><br><span class="line"> topic: 'sometopic',</span><br><span class="line"> data: 'hello world'</span><br><span class="line">});</span><br></pre></td></tr></table></figure> 785 786 <p>And this code snippet shows how to send an object structure:</p> 787 <figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">EmbarkJS.Messages.sendMessage({</span><br><span class="line"> topic: 'sometopic',</span><br><span class="line"> data: { msg: 'hello world' }</span><br><span class="line">});</span><br></pre></td></tr></table></figure> 788 789 <p>Notice that a topic/channel name has to be at least 4 characters long. Whisper will otherwise emit an error on the subscription.</p> 790 <div class="c-notification c-notification--info"> 791 <p><strong>On topic arrays:</strong></p> 792 <p><p>Array of topics are considered an AND. In Whisper you can use another array for OR combinations of several topics e.g <code>["topic1", ["topic2", "topic3"]]</code> => <code>topic1 AND (topic2 OR topic 3)</code>.</p> 793 </p> 794 </div> 795 796 797 798 799 </div> 800 <div class="o-container-medium o-distance-l"> 801 <div class="o-flex o-flex-space-between"> 802 803 <div class="o-flex__item"> 804 <a href="/docs/messages_configuration.html" class="c-button c-button--quite" title="Previous article">Previous</a> 805 </div> 806 807 808 <div class="o-flex__item"> 809 <a href="/docs/naming_configuration.html" class="c-button c-button--quite" title="Next article">Next</a> 810 </div> 811 812 </div> 813 814 815 </div> 816 </div> 817 <div class="o-guided-content__addition"> 818 <h3 class="c-category-title">Contents</h3> 819 <ol class="o-list-bare"><li class="o-list-bare__item o-list-bare-level-2 o-ellipsis"><a href="#Setting-up-EmbarkJS" class="u-link-uniform">Setting up EmbarkJS</a></li><li class="o-list-bare__item o-list-bare-level-2 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