Question

我正在创建一个大学项目，以显示利兹正在发生的事件。我几乎已经完成了使用EventbriteAPI所做的此页面。但是，目前我的页面只有在弄清楚所有事件的场地名称后才需要花费几秒钟的时间才能加载。

我相信我需要使用Promise.all（）函数来实现此目的，但是由于我对此还很陌生，所以我正在努力了解如何实现它。

eventbrite.js

class EventBrite {
    constructor() {
        this.auth_token = 'Example';
        this.orderby = 'date';
        this.city = 'Leeds';
    }

    //Load Leeds events from API
    async loadAPI() {
        const initalEvents = await fetch(`https://www.eventbriteapi.com/v3/events/search/?sort_by=${this.orderby}&location.address=${this.city}&token=${this.auth_token}`);

        const events = await initalEvents.json();

        return {
            events
        }
    }

    async loadVenue(venueID) {
        const initalVenue = await fetch(`https://www.eventbriteapi.com/v3/venues/${venueID}/?token=${this.auth_token}`);

        const venue = await initalVenue.json();

        return venue;
    }
}

app.js

eventbrite.loadAPI()
    .then(async events => {
        //Check for events
        const eventsList = events.events.events;

        //Print venue IDs
        for(let i = 0, l = eventsList.length; i < l; i++) {
            const venueID = eventsList[i].venue_id;

            let venue = await eventbrite.loadVenue(venueID);
            eventsList[i].venue = venue.name
        }
        ui.displayEvents(eventsList);
    }
)

ui.js

class UI {
    constructor() {
        this.init();
    }
    init() {
        this.printCategories();

        this.result = document.getElementById('result');
    }

    //Display events
    displayEvents(events) {   
        //Build template
        let HTMLTemplate = '';
        events.forEach(eventInfo => {
            HTMLTemplate += `
                <div class="row">
                    <div class="column">
                        <p class="event">${eventInfo.name.text}</p>
                        <p class="event">${eventInfo.venue}</p>
                        <p class="event">${eventInfo.start.local}</p>
                    </div>
                </div>
            `;
        });
        this.result.innerHTML = HTMLTemplate;
    }
}

Answer 1

一个问题是，您要依次进行所有这些调用，这意味着完成这些调用的时间加起来了。

最好在paralell中运行它们：

eventbrite.loadAPI()
    .then(async events => {
        let promises = events.events.events.map(async (eventInfo) => {
            let venue = await eventbrite.loadVenue(eventInfo.venue_id);
            eventInfo.venue = venue.name;
            return eventInfo;
        });

        const eventsList = await Promise.all(promises);

        ui.displayEvents(eventsList);
    });

如果响应缓慢返回并且第一个和最后一个之间有很大差异，则可以呈现中间结果：

eventbrite.loadAPI()
    .then(events => {
        const eventsList = events.events.events;

        eventsList.forEach(async (eventInfo) => {
            let venue = await eventbrite.loadVenue(eventInfo.venue_id);
            eventInfo.venue = venue.name;

            ui.displayEvents(eventsList.filter(item => item.venue));
        });
    });

如何使用Promise.all（）函数

1 个答案: