@graffy/common/esm/stream/makeWatcher.js

Common libraries that used by various Graffy modules.

function _createForOfIteratorHelperLoose(o, allowArrayLike) { var it; if (typeof Symbol === "undefined" || o[Symbol.iterator] == null) { if (Array.isArray(o) || (it = _unsupportedIterableToArray(o)) || allowArrayLike && o && typeof o.length === "number") { if (it) o = it; var i = 0; return function () { if (i >= o.length) return { done: true }; return { done: false, value: o[i++] }; }; } throw new TypeError("Invalid attempt to iterate non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method."); } it = o[Symbol.iterator](); return it.next.bind(it); }

function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o === "string") return _arrayLikeToArray(o, minLen); var n = Object.prototype.toString.call(o).slice(8, -1); if (n === "Object" && o.constructor) n = o.constructor.name; if (n === "Map" || n === "Set") return Array.from(o); if (n === "Arguments" || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(n)) return _arrayLikeToArray(o, minLen); }

function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) { arr2[i] = arr[i]; } return arr2; }

import { makeStream } from '@graffy/stream';
export default function makeWatcher() {
  var listeners = new Set();

  function write(change) {
    for (var _iterator = _createForOfIteratorHelperLoose(listeners), _step; !(_step = _iterator()).done;) {
      var push = _step.value;
      push(change);
    }
  }

  function watch() {
    for (var _len = arguments.length, args = new Array(_len), _key = 0; _key < _len; _key++) {
      args[_key] = arguments[_key];
    }

    return makeStream(function (push, _end) {
      listeners.add(push); // We do this instead of binding the first value to a variable
      // to decide between pushing undefined and not making a push.

      if (args.length) Promise.resolve(args[0]).then(push);
      return function () {
        return listeners.delete(push);
      };
    });
  }

  return {
    write: write,
    watch: watch
  };
}