javascript - 在 Node JS 中等待一个函数完成，然后再触发下一个函数

Question

我有这个 gulp 任务:

// default task, runs through all primary tasks
gulp.task("default", ["media", "scripts", "styles", "html"], function () {
    // notify that task is complete
    gulp.src("gulpfile.js")
        .pipe(plugins.gulpif(ran_tasks.length, plugins.notify({title: "Success!", message: ran_tasks.length + " task" + (ran_tasks.length > 1 ? "s" : "") + " complete! [" + ran_tasks.join(", ") + "]", onLast: true})));

    // trigger FTP task if FTP flag is passed
    if (plugins.argv.ftp) {
        config_module.config(gulp, plugins, settings);
        ftp_module.upload(gulp, plugins, settings, ran_tasks, on_error);
    }

    // reset ran_tasks array
    ran_tasks.length = 0;
});

除了 FTP 位之外，效果很好。我需要先完成 config_module.config() ，然后才能触发 ftp_module.upload() 。我尝试过使用回调来设置 promise 和匿名函数，但是这些解决方案都不起作用； FTP 功能在配置之前不断触发。

如何让 ftp_module.upload() 函数在触发之前等待 config_module.config() 完成？

<小时/>

编辑:这是我尝试过的 promise ，但仍然无法正常工作:

new Promise(function (resolve) {
    config_module.config(gulp, plugins, settings);
    resolve();
}).then(function () {
    ftp_module.upload(gulp, plugins, settings, ran_tasks, on_error);
});

<小时/>

编辑:我希望不必发布 modules_config.config() 代码，因为它很长，但我认为有必要继续:

module.exports = {
    // config task, generate configuration file for FTP & BrowserSync and prompt dev for input
    config(gulp, plugins, settings) {
        // generate settings.json and start other functions
        const generate_config = function (callback) {
            return plugins.fs.stat("./settings.json", function (err) {
                if (err !== null) {
                    const json_data =
                    `{
                        "ftp": {
                            "dev": {
                                "hostname": "",
                                "port":     "21",
                                "mode":     "ftp",
                                "username": "",
                                "password": "",
                                "path":     ""
                            },
                            "dist": {
                                "hostname": "",
                                "port":     "21",
                                "mode":     "ftp",
                                "username": "",
                                "password": "",
                                "path":     ""
                            }
                        },
                        "browsersync": {
                            "dev": {
                                "proxy":  "",
                                "port":   "",
                                "open":   "",
                                "notify": ""
                            },
                            "dist": {
                                "proxy":  "",
                                "port":   "",
                                "open":   "",
                                "notify": ""
                            }
                        }
                    }`;

                    plugins.fs.writeFile("./settings.json", json_data, "utf8", function () {
                        callback();
                    });
                } else if (typeof callback === "function") {
                    callback();
                }
            });
        };

        // configue JSON data
        const configure_json = function (namespace, options, env, callback) {
            const prompts = [];

            // construct the prompts
            Object.keys(options).forEach(option => {
                const properties = options[option];

                // construct the prompt
                const prompt     = {
                    name:    option,
                    message: namespace + " " + option + ": ",
                };

                // construct the prompt
                Object.keys(properties).forEach(property => {
                    prompt[property] = properties[property];
                });

                // put the prompt in the array
                prompts.push(prompt);
            });

            // prompt the user
            return gulp.src("./settings.json")
                .pipe(plugins.prompt.prompt(prompts, function (res) {
                    // open settings.json
                    const file = plugins.json.read("./settings.json");

                    // update data in JSON
                    Object.keys(options).forEach(option => {
                        file.set(namespace + "." + env + "." + option, res[option]);
                        settings[namespace][option] = res[option];
                    });

                    // write updated file contents
                    file.writeSync();

                    if (typeof callback === "function") {
                        callback();
                    }
                }));
        };

        return new Promise (function (resolve) {
            // get the target environment
            const env = plugins.argv.dist ? "dist" : "dev";

            // generate settings.json
            generate_config(function () {
                // read browsersync settings from settings.json
                settings.browsersync.proxy  = plugins.json.read("./settings.json").get("browsersync." + env + ".proxy");
                settings.browsersync.port   = plugins.json.read("./settings.json").get("browsersync." + env + ".port");
                settings.browsersync.open   = plugins.json.read("./settings.json").get("browsersync." + env + ".open");
                settings.browsersync.notify = plugins.json.read("./settings.json").get("browsersync." + env + ".notify");

                // read FTP settingss from settings.json
                settings.ftp.host = plugins.json.read("./settings.json").get("ftp." + env + ".hostname");
                settings.ftp.port = plugins.json.read("./settings.json").get("ftp." + env + ".port");
                settings.ftp.mode = plugins.json.read("./settings.json").get("ftp." + env + ".mode");
                settings.ftp.user = plugins.json.read("./settings.json").get("ftp." + env + ".username");
                settings.ftp.pass = plugins.json.read("./settings.json").get("ftp." + env + ".password");
                settings.ftp.path = plugins.json.read("./settings.json").get("ftp." + env + ".path");

                // configure FTP credentials
                configure_json("ftp", {
                    hostname: {
                        default: settings.ftp.host,
                        type:    "input",
                    },
                    port: {
                        default: settings.ftp.port,
                        type:    "input",
                    },
                    mode: {
                        default: settings.ftp.mode === "ftp" ? 0 : settings.ftp.mode === "tls" ? 1 : settings.ftp.mode === "sftp" ? 2 : 0,
                        type:    "list",
                        choices: ["ftp", "tls", "sftp"],
                    },
                    username: {
                        default: settings.ftp.user,
                        type:    "input",
                    },
                    password: {
                        default: settings.ftp.pass,
                        type:    "password",
                    },
                    path: {
                        default: settings.ftp.path,
                        type:    "input",
                    },
                }, env, function () {
                    // configure BrowserSync settings
                    configure_json("browsersync", {
                        proxy: {
                            default: settings.browsersync.proxy === "" ? "localhost" : settings.browsersync.proxy,
                            type: "input",
                        },
                        port: {
                            default: settings.browsersync.port === "" ? "8080" : settings.browsersync.port,
                            type: "input",
                        },
                        open: {
                            default: settings.browsersync.open === "" ? "external" : settings.browsersync.open,
                            type: "input",
                        },
                        notify: {
                            default: settings.browsersync.open === "" ? "false" : settings.browsersync.open,
                            type: "input",
                        },
                    }, env, function () {
                        // resolve the promise
                        resolve();
                    });
                });
            });
        });
    }
};

如您所见，它正在返回一个 promise ，但无论出于何种原因，我仍然无法在其之后触发 FTP 任务。

Answer 1

您的问题已经有了一个可能的答案: promise 。

问题是你做错了。

在您在编辑中发布的代码(带有 promise )中，您正在调用 config_module 方法(这似乎是异步的)，然后立即解决 promise 。在这种情况下，由于该方法是异步的，因此在 config 方法上的处理完成之前，promise 就得到了解决，从而导致了不需要的行为。

正确的方法是您应该 promise config_module 方法调用本身。这样，您只能在方法执行完全完成后“解决” promise 。

很难说 config_module 方法应该如何，因为您没有发布其代码。但是您应该在那里创建一个 promise ，然后仅在计算完成时才解决它。所以你可以这样:

config_module.config(gulp, plugins, settings)
    .then(function () { 
        ftp_module.upload(gulp, plugins, settings, ran_tasks, on_error);
    });

编辑:

发布 config_module 代码后，更容易看出唯一缺少的就是使用 config 方法返回的 Promise 在 .then block 内运行 ftp_module.upload