javascript - 当我从多个地方导入它时如何创建单例类？

Question

如果我想在多个地方导入 Singleton 类，如何制作它？

我最终得到了这样的结果，但每次导入时我都会导出一个 new() 实例(至少我是这么认为的)。

class RenderToRootAPI {
    renderToRootComponent = null
    setRenderComponent = ref => this.renderToRootComponent = ref
    setInstance = instance =>  {
        console.warn('setting instance')
        this.renderToRootComponent.setInstance(instance)
    }
    deleteInstance = () => this.renderToRootComponent.deleteInstance
}

export default new RenderToRootAPI()

Answer 1

您所编写的将导出一个单例。导入多少次并不重要。

如果你像这样写作为例子，可能看起来更清楚一点:

class RenderToRootAPI {
    renderToRootComponent = null
    setRenderComponent = ref => this.renderToRootComponent = ref
    setInstance = instance =>  {
        console.warn('setting instance')
        this.renderToRootComponent.setInstance(instance)
    }
    deleteInstance = () => this.renderToRootComponent.deleteInstance
}

const renderToRootAPI = new RenderToRootAPI();

export default renderToRootAPI;

该类甚至没有导出，单个导出的实例将在导入它的所有模块中使用。