javascript - console.log 返回待处理的 promise ，而不是实际数据

Question

这个问题已经有答案了:

How do I return the response from an asynchronous call? (42 个回答)

已关闭 6 年前。

所以我有这个文件:

 'use strict'
import * as moment from "moment";
import { Report} from "./Report";
import { Timeframe} from "./Timeframe";
import { ReportComparison } from "./ReportComparison";

function test(firstFrom: string, firstTo: string, secondFrom: string, secondTo: string) {


    var pastReport = new Report(new Timeframe(moment(firstFrom), moment(firstTo)));
    var laterReport = new Report(new Timeframe(moment(secondFrom), moment(secondTo)));

    var reportComparison

    function getData(pastReport: Report, laterReport: Report) {

        var later = function() {
            return new Promise((resolve, reject) => {
                laterReport.fetchData(data => resolve(data));
            });
        };

        var past = function() {
            return new Promise((resolve, reject) => {
                pastReport.fetchData(data => resolve(data));
            });
        };

        return Promise.all([later(), past()]).then(() => {
            laterReport.sort();
            reportComparison = new ReportComparison(pastReport, laterReport);

            return {
                pastReport: {
                    projects: reportComparison.pastReport.projects,
                    timeFrame: reportComparison.pastReport.timeframe,
                    totalAutomatedRuns: reportComparison.pastReport.totalAutomatedRuns,
                    totalManualRuns: reportComparison.pastReport.totalManualRuns

                },
                laterReport: {
                    projects: reportComparison.laterReport.projects,
                    timeFrame: reportComparison.laterReport.timeframe,
                    totalAutomatedRuns: reportComparison.laterReport.totalAutomatedRuns,
                    totalManualRuns: reportComparison.laterReport.totalManualRuns
                },
                trends: reportComparison.trends
            }

        });

    }

    return getData(pastReport, laterReport).then((res) => {
        return res;
    });

}



console.log(test("20170707", "20170707", "20170710", "20170710"))

现在，console.log 返回 Promise { <pending> }而不是我想要返回的实际值(JSON 对象)。我是否正确地处理了这个异步代码？我可以使用什么解决方案将 JSON 作为值返回，而不是待处理的 promise 。

Answer 1

是的，只有当你从这里返回 promise 时，你才会得到 promise

return getData(pastReport, laterReport).then((res) => {

    return res; //Do callback here...
});

这是您的主要返回值，我的意思是测试函数的返回值，并且您仅返回了 Promise，并注意您从那时返回的内容将仅在该函数中返回，因此它不会反射(reflect)在测试的返回值中。如果您不想更改代码，可以使用回调

或将其更改为

return getData(pastReport, laterReport)

并像这样进行测试调用

test(...).then((res)=>{ 
})
Or like this
var a = await test(...)
then test will return data.