All files / lib/internal event_target.js

100% Statements 1002/1002
98.07% Branches 255/260
100% Functions 63/63
100% Lines 1002/1002

Press n or j to go to the next uncovered block, b, p or k for the previous block.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 100351x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 5x 5x 51x 51x 70977x 70977x 70977x 51x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 35501x 35501x 35498x 35498x 35498x 35498x 35498x 35498x 35498x 35498x 35498x 35501x 559x 559x 35493x 35493x 35493x 35493x 35493x 35493x 35493x 35493x 35493x 35493x 35501x 25284x 25284x 2x 2x 2x 2x 2x 1x 1x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 25284x 25284x 8x 8x 7x 8x 25284x 25284x 15x 15x 14x 15x 25284x 25284x 25284x 25284x 25284x 17x 17x 16x 17x 25284x 25284x 25284x 25284x 25284x 4x 4x 3x 4x 25284x 25284x 25284x 25284x 25284x 4x 4x 3x 4x 25284x 25284x 25284x 25284x 25284x 35439x 35439x 35438x 35439x 25284x 25284x 25284x 25284x 25284x 12x 12x 11x 12x 25284x 25284x 25284x 25284x 25284x 35407x 35407x 35407x 35407x 25284x 25284x 25284x 25284x 25284x 4x 4x 3x 4x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 25284x 8x 8x 8x 8x 25284x 25284x 25284x 25284x 25284x 4x 4x 3x 4x 25284x 25284x 25284x 25284x 25284x 12x 12x 11x 12x 25284x 25284x 25284x 25284x 25284x 2x 2x 1x 2x 25284x 25284x 25284x 25284x 25284x 14x 14x 14x 14x 25284x 25284x 25284x 25284x 25284x 14x 14x 13x 14x 25284x 25284x 25284x 25284x 25284x 4x 4x 4x 4x 4x 4x 25284x 25284x 7x 7x 6x 7x 25284x 25284x 25284x 25284x 25284x 25284x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 2x 2x 2x 2x 2x 51x 51x 51x 51x 51x 51x 51x 51x 85x 85x 85x 85x 85x 85x 85x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 120785x 30x 30x 30x 30x 30x 120785x 120741x 120741x 120755x 14x 12x 12x 14x 14x 14x 120785x 51x 51x 20351x 20351x 20351x 51x 51x 40398x 40398x 40398x 40398x 40398x 40398x 40398x 40398x 51x 51x 40103x 40103x 40103x 40103x 40103x 51x 51x 51x 51x 51x 51x 51x 51x 2889x 2889x 51x 51x 120787x 120787x 120787x 5x 5x 5x 5x 5x 5x 5x 5x 5x 5x 5x 5x 5x 120787x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 120819x 120819x 120818x 120818x 120816x 120816x 120816x 120816x 120816x 120816x 120816x 120816x 120816x 120816x 120816x 120816x 120818x 10x 10x 10x 10x 10x 10x 10x 10x 10x 10x 10x 120796x 120796x 120818x 26x 2x 2x 24x 24x 24x 20x 24x 24x 120794x 120794x 120794x 120813x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 110707x 10087x 10087x 10087x 10087x 10087x 120819x 89x 89x 89x 10087x 80550x 9x 9x 10078x 10078x 10078x 10078x 10078x 120819x 51x 51x 51x 51x 51x 51x 51x 51x 51x 20306x 20306x 20305x 20305x 20295x 20295x 20306x 20306x 20306x 20306x 20306x 20248x 20248x 20258x 20253x 20248x 20248x 20248x 20248x 20248x 20248x 20248x 5x 5x 20306x 51x 51x 51x 51x 51x 35391x 35391x 35381x 35381x 35390x 35376x 35376x 35390x 35375x 35375x 35375x 35375x 35391x 51x 51x 97548x 388x 79x 79x 79x 79x 388x 97548x 97548x 35375x 35375x 35375x 97548x 97548x 97548x 35078x 35078x 35078x 35078x 62470x 62470x 62470x 62470x 97480x 97548x 62518x 62518x 62518x 62518x 3x 3x 3x 3x 3x 62518x 20147x 20147x 20147x 20147x 20147x 62515x 62515x 62515x 62518x 62127x 62511x 388x 388x 62518x 62518x 62518x 62518x 62514x 62514x 386x 386x 62514x 62518x 62518x 62518x 50x 50x 62491x 62491x 62491x 62446x 62446x 97087x 97548x 51x 51x 2x 2x 51x 3x 3x 3x 3x 3x 1x 1x 3x 3x 3x 3x 3x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 37214x 37214x 37214x 51x 51x 51x 51x 51x 51x 13x 13x 13x 51x 51x 51x 51x 51x 2x 2x 1x 2x 51x 51x 51x 51x 51x 2x 2x 1x 2x 51x 51x 51x 51x 51x 8x 8x 7x 8x 51x 51x 51x 51x 51x 51x 28x 28x 27x 28x 28x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 104x 104x 103x 103x 104x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 20010x 20010x 20009x 20009x 20010x 51x 51x 51x 51x 51x 51x 51x 80217x 80217x 80216x 80216x 80217x 51x 51x 51x 51x 51x 51x 51x 4x 4x 3x 3x 4x 51x 51x 51x 51x 51x 51x 51x 4x 4x 3x 3x 3x 3x 4x 51x 51x 51x 51x 51x 51x 51x 40063x 40063x 40062x 40062x 40062x 40063x 51x 51x 51x 51x 51x 51x 3x 3x 2x 1x 1x 1x 1x 2x 2x 3x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 141121x 141121x 141121x 141082x 141082x 38x 38x 104x 18x 77x 9x 9x 9x 9x 9x 141121x 51x 120816x 120816x 120816x 120812x 120812x 120816x 120811x 120811x 120811x 120811x 120811x 120811x 120811x 120811x 120811x 120811x 120811x 120816x 51x 51x 51x 51x 51x 51x 176575x 176575x 176575x 51x 140445x 140445x 140445x 51x 15451x 15451x 15451x 14x 3x 3x 3x 14x 14x 15451x 51x 53x 53x 53x 51x 149x 149x 149x 149x 115x 1x 1x 114x 115x 149x 149x 149x 51x 6212x 6212x 6212x 6212x 6212x 3x 6212x 6212x 155x 109x 109x 155x 155x 6x 6x 6x 6x 6x 6x 6x 2x 2x 2x 2x 155x 149x 149x 149x 155x 6212x 6212x 6212x 6212x 6212x 51x 51x 6428x 6428x 1259x 1259x 1259x 1259x 6428x 6428x 6428x 6428x 6428x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x 51x  
'use strict';
 
const {
  ArrayFrom,
  Boolean,
  Error,
  FunctionPrototypeCall,
  NumberIsInteger,
  ObjectAssign,
  ObjectDefineProperties,
  ObjectDefineProperty,
  ObjectGetOwnPropertyDescriptor,
  ObjectGetOwnPropertyDescriptors,
  ReflectApply,
  SafeArrayIterator,
  SafeFinalizationRegistry,
  SafeMap,
  SafeWeakMap,
  SafeWeakRef,
  SafeWeakSet,
  String,
  Symbol,
  SymbolFor,
  SymbolToStringTag,
} = primordials;
 
const {
  codes: {
    ERR_INVALID_ARG_TYPE,
    ERR_EVENT_RECURSION,
    ERR_MISSING_ARGS,
    ERR_INVALID_THIS,
  }
} = require('internal/errors');
const { validateObject, validateString } = require('internal/validators');
 
const {
  customInspectSymbol,
  kEmptyObject,
  kEnumerableProperty,
} = require('internal/util');
const { inspect } = require('util');
 
const kIsEventTarget = SymbolFor('nodejs.event_target');
const kIsNodeEventTarget = Symbol('kIsNodeEventTarget');
 
const EventEmitter = require('events');
const {
  kMaxEventTargetListeners,
  kMaxEventTargetListenersWarned,
} = EventEmitter;
 
const kEvents = Symbol('kEvents');
const kIsBeingDispatched = Symbol('kIsBeingDispatched');
const kStop = Symbol('kStop');
const kTarget = Symbol('kTarget');
const kHandlers = Symbol('khandlers');
const kWeakHandler = Symbol('kWeak');
 
const kHybridDispatch = SymbolFor('nodejs.internal.kHybridDispatch');
const kCreateEvent = Symbol('kCreateEvent');
const kNewListener = Symbol('kNewListener');
const kRemoveListener = Symbol('kRemoveListener');
const kIsNodeStyleListener = Symbol('kIsNodeStyleListener');
const kTrustEvent = Symbol('kTrustEvent');
 
const { now } = require('internal/perf/utils');
 
const kType = Symbol('type');
 
const isTrustedSet = new SafeWeakSet();
const isTrusted = ObjectGetOwnPropertyDescriptor({
  get isTrusted() {
    return isTrustedSet.has(this);
  }
}, 'isTrusted').get;
 
function isEvent(value) {
  return typeof value?.[kType] === 'string';
}
 
class Event {
  #cancelable = false;
  #bubbles = false;
  #composed = false;
  #defaultPrevented = false;
  #timestamp = now();
  #propagationStopped = false;
 
  /**
   * @param {string} type
   * @param {{
   *   bubbles?: boolean,
   *   cancelable?: boolean,
   *   composed?: boolean,
   * }} [options]
   */
  constructor(type, options = null) {
    if (arguments.length === 0)
      throw new ERR_MISSING_ARGS('type');
    validateObject(options, 'options', {
      allowArray: true, allowFunction: true, nullable: true,
    });
    const { cancelable, bubbles, composed } = { ...options };
    this.#cancelable = !!cancelable;
    this.#bubbles = !!bubbles;
    this.#composed = !!composed;
 
    this[kType] = `${type}`;
    if (options?.[kTrustEvent]) {
      isTrustedSet.add(this);
    }
 
    // isTrusted is special (LegacyUnforgeable)
    ObjectDefineProperty(this, 'isTrusted', {
      __proto__: null,
      get: isTrusted,
      enumerable: true,
      configurable: false
    });
    this[kTarget] = null;
    this[kIsBeingDispatched] = false;
  }
 
  [customInspectSymbol](depth, options) {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    const name = this.constructor.name;
    if (depth < 0)
      return name;
 
    const opts = ObjectAssign({}, options, {
      depth: NumberIsInteger(options.depth) ? options.depth - 1 : options.depth
    });
 
    return `${name} ${inspect({
      type: this[kType],
      defaultPrevented: this.#defaultPrevented,
      cancelable: this.#cancelable,
      timeStamp: this.#timestamp,
    }, opts)}`;
  }
 
  stopImmediatePropagation() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    this[kStop] = true;
  }
 
  preventDefault() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    this.#defaultPrevented = true;
  }
 
  /**
   * @type {EventTarget}
   */
  get target() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this[kTarget];
  }
 
  /**
   * @type {EventTarget}
   */
  get currentTarget() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this[kTarget];
  }
 
  /**
   * @type {EventTarget}
   */
  get srcElement() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this[kTarget];
  }
 
  /**
   * @type {string}
   */
  get type() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this[kType];
  }
 
  /**
   * @type {boolean}
   */
  get cancelable() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this.#cancelable;
  }
 
  /**
   * @type {boolean}
   */
  get defaultPrevented() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this.#cancelable && this.#defaultPrevented;
  }
 
  /**
   * @type {number}
   */
  get timeStamp() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this.#timestamp;
  }
 
 
  // The following are non-op and unused properties/methods from Web API Event.
  // These are not supported in Node.js and are provided purely for
  // API completeness.
  /**
   * @returns {EventTarget[]}
   */
  composedPath() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this[kIsBeingDispatched] ? [this[kTarget]] : [];
  }
 
  /**
   * @type {boolean}
   */
  get returnValue() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return !this.defaultPrevented;
  }
 
  /**
   * @type {boolean}
   */
  get bubbles() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this.#bubbles;
  }
 
  /**
   * @type {boolean}
   */
  get composed() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this.#composed;
  }
 
  /**
   * @type {number}
   */
  get eventPhase() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this[kIsBeingDispatched] ? Event.AT_TARGET : Event.NONE;
  }
 
  /**
   * @type {boolean}
   */
  get cancelBubble() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    return this.#propagationStopped;
  }
 
  /**
   * @type {boolean}
   */
  set cancelBubble(value) {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    if (value) {
      this.stopPropagation();
    }
  }
 
  stopPropagation() {
    if (!isEvent(this))
      throw new ERR_INVALID_THIS('Event');
    this.#propagationStopped = true;
  }
 
  static NONE = 0;
  static CAPTURING_PHASE = 1;
  static AT_TARGET = 2;
  static BUBBLING_PHASE = 3;
}
 
ObjectDefineProperties(
  Event.prototype, {
    [SymbolToStringTag]: {
      __proto__: null,
      writable: false,
      enumerable: false,
      configurable: true,
      value: 'Event',
    },
    stopImmediatePropagation: kEnumerableProperty,
    preventDefault: kEnumerableProperty,
    target: kEnumerableProperty,
    currentTarget: kEnumerableProperty,
    srcElement: kEnumerableProperty,
    type: kEnumerableProperty,
    cancelable: kEnumerableProperty,
    defaultPrevented: kEnumerableProperty,
    timeStamp: kEnumerableProperty,
    composedPath: kEnumerableProperty,
    returnValue: kEnumerableProperty,
    bubbles: kEnumerableProperty,
    composed: kEnumerableProperty,
    eventPhase: kEnumerableProperty,
    cancelBubble: kEnumerableProperty,
    stopPropagation: kEnumerableProperty,
  });
 
class NodeCustomEvent extends Event {
  constructor(type, options) {
    super(type, options);
    if (options?.detail) {
      this.detail = options.detail;
    }
  }
}
 
// Weak listener cleanup
// This has to be lazy for snapshots to work
let weakListenersState = null;
// The resource needs to retain the callback so that it doesn't
// get garbage collected now that it's weak.
let objectToWeakListenerMap = null;
function weakListeners() {
  weakListenersState ??= new SafeFinalizationRegistry(
    (listener) => listener.remove()
  );
  objectToWeakListenerMap ??= new SafeWeakMap();
  return { registry: weakListenersState, map: objectToWeakListenerMap };
}
 
// The listeners for an EventTarget are maintained as a linked list.
// Unfortunately, the way EventTarget is defined, listeners are accounted
// using the tuple [handler,capture], and even if we don't actually make
// use of capture or bubbling, in order to be spec compliant we have to
// take on the additional complexity of supporting it. Fortunately, using
// the linked list makes dispatching faster, even if adding/removing is
// slower.
class Listener {
  constructor(previous, listener, once, capture, passive,
              isNodeStyleListener, weak) {
    this.next = undefined;
    if (previous !== undefined)
      previous.next = this;
    this.previous = previous;
    this.listener = listener;
    // TODO(benjamingr) these 4 can be 'flags' to save 3 slots
    this.once = once;
    this.capture = capture;
    this.passive = passive;
    this.isNodeStyleListener = isNodeStyleListener;
    this.removed = false;
    this.weak = Boolean(weak); // Don't retain the object
 
    if (this.weak) {
      this.callback = new SafeWeakRef(listener);
      weakListeners().registry.register(listener, this, this);
      // Make the retainer retain the listener in a WeakMap
      weakListeners().map.set(weak, listener);
      this.listener = this.callback;
    } else if (typeof listener === 'function') {
      this.callback = listener;
      this.listener = listener;
    } else {
      this.callback = async (...args) => {
        if (listener.handleEvent)
          await ReflectApply(listener.handleEvent, listener, args);
      };
      this.listener = listener;
    }
  }
 
  same(listener, capture) {
    const myListener = this.weak ? this.listener.deref() : this.listener;
    return myListener === listener && this.capture === capture;
  }
 
  remove() {
    if (this.previous !== undefined)
      this.previous.next = this.next;
    if (this.next !== undefined)
      this.next.previous = this.previous;
    this.removed = true;
    if (this.weak)
      weakListeners().registry.unregister(this);
  }
}
 
function initEventTarget(self) {
  self[kEvents] = new SafeMap();
  self[kMaxEventTargetListeners] = EventEmitter.defaultMaxListeners;
  self[kMaxEventTargetListenersWarned] = false;
}
 
class EventTarget {
  // Used in checking whether an object is an EventTarget. This is a well-known
  // symbol as EventTarget may be used cross-realm.
  // Ref: https://github.com/nodejs/node/pull/33661
  static [kIsEventTarget] = true;
 
  constructor() {
    initEventTarget(this);
  }
 
  [kNewListener](size, type, listener, once, capture, passive, weak) {
    if (this[kMaxEventTargetListeners] > 0 &&
        size > this[kMaxEventTargetListeners] &&
        !this[kMaxEventTargetListenersWarned]) {
      this[kMaxEventTargetListenersWarned] = true;
      // No error code for this since it is a Warning
      // eslint-disable-next-line no-restricted-syntax
      const w = new Error('Possible EventTarget memory leak detected. ' +
                          `${size} ${type} listeners ` +
                          `added to ${inspect(this, { depth: -1 })}. Use ` +
                          'events.setMaxListeners() to increase limit');
      w.name = 'MaxListenersExceededWarning';
      w.target = this;
      w.type = type;
      w.count = size;
      process.emitWarning(w);
    }
  }
  [kRemoveListener](size, type, listener, capture) {}
 
  /**
   * @callback EventTargetCallback
   * @param {Event} event
   */
 
  /**
   * @typedef {{ handleEvent: EventTargetCallback }} EventListener
   */
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @param {{
   *   capture?: boolean,
   *   once?: boolean,
   *   passive?: boolean,
   *   signal?: AbortSignal
   * }} [options]
   */
  addEventListener(type, listener, options = kEmptyObject) {
    if (!isEventTarget(this))
      throw new ERR_INVALID_THIS('EventTarget');
    if (arguments.length < 2)
      throw new ERR_MISSING_ARGS('type', 'listener');
 
    // We validateOptions before the validateListener check because the spec
    // requires us to hit getters.
    const {
      once,
      capture,
      passive,
      signal,
      isNodeStyleListener,
      weak,
    } = validateEventListenerOptions(options);
 
    if (!validateEventListener(listener)) {
      // The DOM silently allows passing undefined as a second argument
      // No error code for this since it is a Warning
      // eslint-disable-next-line no-restricted-syntax
      const w = new Error(`addEventListener called with ${listener}` +
                          ' which has no effect.');
      w.name = 'AddEventListenerArgumentTypeWarning';
      w.target = this;
      w.type = type;
      process.emitWarning(w);
      return;
    }
    type = String(type);
 
    if (signal) {
      if (signal.aborted) {
        return;
      }
      // TODO(benjamingr) make this weak somehow? ideally the signal would
      // not prevent the event target from GC.
      signal.addEventListener('abort', () => {
        this.removeEventListener(type, listener, options);
      }, { once: true, [kWeakHandler]: this });
    }
 
    let root = this[kEvents].get(type);
 
    if (root === undefined) {
      root = { size: 1, next: undefined };
      // This is the first handler in our linked list.
      new Listener(root, listener, once, capture, passive,
                   isNodeStyleListener, weak);
      this[kNewListener](
        root.size,
        type,
        listener,
        once,
        capture,
        passive,
        weak);
      this[kEvents].set(type, root);
      return;
    }
 
    let handler = root.next;
    let previous = root;
 
    // We have to walk the linked list to see if we have a match
    while (handler !== undefined && !handler.same(listener, capture)) {
      previous = handler;
      handler = handler.next;
    }
 
    if (handler !== undefined) { // Duplicate! Ignore
      return;
    }
 
    new Listener(previous, listener, once, capture, passive,
                 isNodeStyleListener, weak);
    root.size++;
    this[kNewListener](root.size, type, listener, once, capture, passive, weak);
  }
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @param {{
   *   capture?: boolean,
   * }} [options]
   */
  removeEventListener(type, listener, options = kEmptyObject) {
    if (!isEventTarget(this))
      throw new ERR_INVALID_THIS('EventTarget');
    if (!validateEventListener(listener))
      return;
 
    type = String(type);
    const capture = options?.capture === true;
 
    const root = this[kEvents].get(type);
    if (root === undefined || root.next === undefined)
      return;
 
    let handler = root.next;
    while (handler !== undefined) {
      if (handler.same(listener, capture)) {
        handler.remove();
        root.size--;
        if (root.size === 0)
          this[kEvents].delete(type);
        this[kRemoveListener](root.size, type, listener, capture);
        break;
      }
      handler = handler.next;
    }
  }
 
  /**
   * @param {Event} event
   */
  dispatchEvent(event) {
    if (!isEventTarget(this))
      throw new ERR_INVALID_THIS('EventTarget');
 
    if (!(event instanceof Event))
      throw new ERR_INVALID_ARG_TYPE('event', 'Event', event);
 
    if (event[kIsBeingDispatched])
      throw new ERR_EVENT_RECURSION(event.type);
 
    this[kHybridDispatch](event, event.type, event);
 
    return event.defaultPrevented !== true;
  }
 
  [kHybridDispatch](nodeValue, type, event) {
    const createEvent = () => {
      if (event === undefined) {
        event = this[kCreateEvent](nodeValue, type);
        event[kTarget] = this;
        event[kIsBeingDispatched] = true;
      }
      return event;
    };
    if (event !== undefined) {
      event[kTarget] = this;
      event[kIsBeingDispatched] = true;
    }
 
    const root = this[kEvents].get(type);
    if (root === undefined || root.next === undefined) {
      if (event !== undefined)
        event[kIsBeingDispatched] = false;
      return true;
    }
 
    let handler = root.next;
    let next;
 
    while (handler !== undefined &&
           (handler.passive || event?.[kStop] !== true)) {
      // Cache the next item in case this iteration removes the current one
      next = handler.next;
 
      if (handler.removed) {
        // Deal with the case an event is removed while event handlers are
        // Being processed (removeEventListener called from a listener)
        handler = next;
        continue;
      }
      if (handler.once) {
        handler.remove();
        root.size--;
        const { listener, capture } = handler;
        this[kRemoveListener](root.size, type, listener, capture);
      }
 
      try {
        let arg;
        if (handler.isNodeStyleListener) {
          arg = nodeValue;
        } else {
          arg = createEvent();
        }
        const callback = handler.weak ?
          handler.callback.deref() : handler.callback;
        let result;
        if (callback) {
          result = FunctionPrototypeCall(callback, this, arg);
          if (!handler.isNodeStyleListener) {
            arg[kIsBeingDispatched] = false;
          }
        }
        if (result !== undefined && result !== null)
          addCatch(result);
      } catch (err) {
        emitUncaughtException(err);
      }
 
      handler = next;
    }
 
    if (event !== undefined)
      event[kIsBeingDispatched] = false;
  }
 
  [kCreateEvent](nodeValue, type) {
    return new NodeCustomEvent(type, { detail: nodeValue });
  }
  [customInspectSymbol](depth, options) {
    if (!isEventTarget(this))
      throw new ERR_INVALID_THIS('EventTarget');
    const name = this.constructor.name;
    if (depth < 0)
      return name;
 
    const opts = ObjectAssign({}, options, {
      depth: NumberIsInteger(options.depth) ? options.depth - 1 : options.depth
    });
 
    return `${name} ${inspect({}, opts)}`;
  }
}
 
ObjectDefineProperties(EventTarget.prototype, {
  addEventListener: kEnumerableProperty,
  removeEventListener: kEnumerableProperty,
  dispatchEvent: kEnumerableProperty,
  [SymbolToStringTag]: {
    __proto__: null,
    writable: false,
    enumerable: false,
    configurable: true,
    value: 'EventTarget',
  }
});
 
function initNodeEventTarget(self) {
  initEventTarget(self);
}
 
class NodeEventTarget extends EventTarget {
  static [kIsNodeEventTarget] = true;
  static defaultMaxListeners = 10;
 
  constructor() {
    super();
    initNodeEventTarget(this);
  }
 
  /**
   * @param {number} n
   */
  setMaxListeners(n) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    EventEmitter.setMaxListeners(n, this);
  }
 
  /**
   * @returns {number}
   */
  getMaxListeners() {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    return this[kMaxEventTargetListeners];
  }
 
  /**
   * @returns {string[]}
   */
  eventNames() {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    return ArrayFrom(this[kEvents].keys());
  }
 
  /**
   * @param {string} [type]
   * @returns {number}
   */
  listenerCount(type) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    const root = this[kEvents].get(String(type));
    return root !== undefined ? root.size : 0;
  }
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @param {{
   *   capture?: boolean,
   * }} [options]
   * @returns {NodeEventTarget}
   */
  off(type, listener, options) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    this.removeEventListener(type, listener, options);
    return this;
  }
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @param {{
   *   capture?: boolean,
   * }} [options]
   * @returns {NodeEventTarget}
   */
  removeListener(type, listener, options) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    this.removeEventListener(type, listener, options);
    return this;
  }
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @returns {NodeEventTarget}
   */
  on(type, listener) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    this.addEventListener(type, listener, { [kIsNodeStyleListener]: true });
    return this;
  }
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @returns {NodeEventTarget}
   */
  addListener(type, listener) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    this.addEventListener(type, listener, { [kIsNodeStyleListener]: true });
    return this;
  }
 
  /**
   * @param {string} type
   * @param {any} arg
   * @returns {boolean}
   */
  emit(type, arg) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    validateString(type, 'type');
    const hadListeners = this.listenerCount(type) > 0;
    this[kHybridDispatch](arg, type);
    return hadListeners;
  }
 
  /**
   * @param {string} type
   * @param {EventTargetCallback|EventListener} listener
   * @returns {NodeEventTarget}
   */
  once(type, listener) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    this.addEventListener(type, listener,
                          { once: true, [kIsNodeStyleListener]: true });
    return this;
  }
 
  /**
   * @param {string} type
   * @returns {NodeEventTarget}
   */
  removeAllListeners(type) {
    if (!isNodeEventTarget(this))
      throw new ERR_INVALID_THIS('NodeEventTarget');
    if (type !== undefined) {
      this[kEvents].delete(String(type));
    } else {
      this[kEvents].clear();
    }
 
    return this;
  }
}
 
ObjectDefineProperties(NodeEventTarget.prototype, {
  setMaxListeners: kEnumerableProperty,
  getMaxListeners: kEnumerableProperty,
  eventNames: kEnumerableProperty,
  listenerCount: kEnumerableProperty,
  off: kEnumerableProperty,
  removeListener: kEnumerableProperty,
  on: kEnumerableProperty,
  addListener: kEnumerableProperty,
  once: kEnumerableProperty,
  emit: kEnumerableProperty,
  removeAllListeners: kEnumerableProperty,
});
 
// EventTarget API
 
function validateEventListener(listener) {
  if (typeof listener === 'function' ||
      typeof listener?.handleEvent === 'function') {
    return true;
  }
 
  if (listener == null)
    return false;
 
  if (typeof listener === 'object') {
    // Require `handleEvent` lazily.
    return true;
  }
 
  throw new ERR_INVALID_ARG_TYPE('listener', 'EventListener', listener);
}
 
function validateEventListenerOptions(options) {
  if (typeof options === 'boolean')
    return { capture: options };
 
  if (options === null)
    return kEmptyObject;
  validateObject(options, 'options', {
    allowArray: true, allowFunction: true,
  });
  return {
    once: Boolean(options.once),
    capture: Boolean(options.capture),
    passive: Boolean(options.passive),
    signal: options.signal,
    weak: options[kWeakHandler],
    isNodeStyleListener: Boolean(options[kIsNodeStyleListener])
  };
}
 
// Test whether the argument is an event object. This is far from a fool-proof
// test, for example this input will result in a false positive:
// > isEventTarget({ constructor: EventTarget })
// It stands in its current implementation as a compromise.
// Ref: https://github.com/nodejs/node/pull/33661
function isEventTarget(obj) {
  return obj?.constructor?.[kIsEventTarget];
}
 
function isNodeEventTarget(obj) {
  return obj?.constructor?.[kIsNodeEventTarget];
}
 
function addCatch(promise) {
  const then = promise.then;
  if (typeof then === 'function') {
    FunctionPrototypeCall(then, promise, undefined, function(err) {
      // The callback is called with nextTick to avoid a follow-up
      // rejection from this promise.
      emitUncaughtException(err);
    });
  }
}
 
function emitUncaughtException(err) {
  process.nextTick(() => { throw err; });
}
 
function makeEventHandler(handler) {
  // Event handlers are dispatched in the order they were first set
  // See https://github.com/nodejs/node/pull/35949#issuecomment-722496598
  function eventHandler(...args) {
    if (typeof eventHandler.handler !== 'function') {
      return;
    }
    return ReflectApply(eventHandler.handler, this, args);
  }
  eventHandler.handler = handler;
  return eventHandler;
}
 
function defineEventHandler(emitter, name) {
  // 8.1.5.1 Event handlers - basically `on[eventName]` attributes
  ObjectDefineProperty(emitter, `on${name}`, {
    __proto__: null,
    get() {
      return this[kHandlers]?.get(name)?.handler ?? null;
    },
    set(value) {
      if (!this[kHandlers]) {
        this[kHandlers] = new SafeMap();
      }
      let wrappedHandler = this[kHandlers]?.get(name);
      if (wrappedHandler) {
        if (typeof wrappedHandler.handler === 'function') {
          this[kEvents].get(name).size--;
          const size = this[kEvents].get(name).size;
          this[kRemoveListener](size, name, wrappedHandler.handler, false);
        }
        wrappedHandler.handler = value;
        if (typeof wrappedHandler.handler === 'function') {
          this[kEvents].get(name).size++;
          const size = this[kEvents].get(name).size;
          this[kNewListener](size, name, value, false, false, false, false);
        }
      } else {
        wrappedHandler = makeEventHandler(value);
        this.addEventListener(name, wrappedHandler);
      }
      this[kHandlers].set(name, wrappedHandler);
    },
    configurable: true,
    enumerable: true
  });
}
 
const EventEmitterMixin = (Superclass) => {
  class MixedEventEmitter extends Superclass {
    constructor(...args) {
      args = new SafeArrayIterator(args);
      super(...args);
      FunctionPrototypeCall(EventEmitter, this);
    }
  }
  const protoProps = ObjectGetOwnPropertyDescriptors(EventEmitter.prototype);
  delete protoProps.constructor;
  ObjectDefineProperties(MixedEventEmitter.prototype, protoProps);
  return MixedEventEmitter;
};
 
module.exports = {
  Event,
  EventEmitterMixin,
  EventTarget,
  NodeEventTarget,
  defineEventHandler,
  initEventTarget,
  initNodeEventTarget,
  kCreateEvent,
  kNewListener,
  kTrustEvent,
  kRemoveListener,
  kEvents,
  kWeakHandler,
  isEventTarget,
};