vscroll/dist/esm2015/classes/reactive.js

Virtual scroll engine

export class Reactive {
  constructor(value, options) {
    this.id = 0;
    if (value !== void 0) {
      this.value = value;
      this.initialValue = value;
    }
    this.options = options || {};
    this.subscriptions = new Map();
  }
  set(value) {
    if (this.value === value && !this.options.emitEqual) {
      return;
    }
    this.value = value;
    for (const [, sub] of this.subscriptions) {
      sub.emit(value);
      if (this.value !== value) {
        break;
      }
    }
  }
  get() {
    return this.value;
  }
  on(func) {
    const id = this.id++;
    const subscription = {
      emit: func,
      off: () => {
        subscription.emit = () => null;
        this.subscriptions.delete(id);
      }
    };
    this.subscriptions.set(id, subscription);
    if (this.options.emitOnSubscribe) {
      subscription.emit(this.value);
    }
    return () => subscription.off();
  }
  once(func) {
    const off = this.on(v => {
      off();
      func(v);
    });
    return off;
  }
  reset() {
    this.set(this.initialValue);
  }
  dispose() {
    this.subscriptions.forEach(sub => sub.off());
  }
}
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