Question

我想使用Promises以同步顺序执行我的任务，为此，我有以下3个函数：

init（）：我的承诺是对此进行管理;
saveUser（）：将用户对象保存到数据库中的函数;
负责以同步顺序运行它的主要功能。

没有通过'user'变量，它工作正常。我想知道，如何将此“用户”变量传递到我的saveUser.bind()以运行到我的承诺中并由userSave()函数保存？

// promise function
function init(fn) {
  return new Promise((resolve, reject) => {
    fn((err, result) => {
      if (err) reject(err);
      console.log('the saveUser function ran inside my promise...');
      resolve(result);
    });
  });
}

// saveUser function, need receive the user variable and show in console log
function saveUser(callback, user) {
  console.log('1. the user will be save...', user);
  setTimeout(() => {
    console.log('2. the user was saved!');
    return callback(null, true);
  }, 1000);
}

// main function that I need to pass the user variable into saveUser() function
let user = {name: 'Rick'};
init(saveUser.bind(x => x)).
  then(() => console.log('3. Promise finished with success!')).
  catch((err) => console.log('3. Promise was rejected!', err));

Answer 1

第一个绑定参数是this 绑定代码将如下所示。 saveUser.bind(x=>x, x=>x, user)

＆＃13;

// promise function
function init(fn) {
  return new Promise((resolve, reject) => {
    fn(resolve,reject);
  });
}

// saveUser function, need receive the user variable and show in console log
function saveUser(callback, user,resolve,reject) {
  console.log('1. the user will be save...', user);
  setTimeout(() => {
    console.log('2. the user was saved!');
    resolve(callback(null, true));
  }, 1000);
}

// main function that I need to pass the user variable into saveUser() function
let user = {name: 'Rick'};
init(saveUser.bind(this, x=>x, user)).
  then(() => console.log('3. Promise finished with success!')).
  catch((err) => console.log('3. Promise was rejected!', err));

＆＃13;

Answer 2

我不确定是否确切地如何整理这个东西，但是在那里，你的代码片段正在工作

＆＃13;

// promise function
function init(fn, thisArg, ...params) {
  return new Promise((resolve, reject) => {
    fn.apply(thisArg, [(err, res) => {
      console.log('the saveUser function ran inside my promise...');
    }, ...params]).then((data) => {
      resolve(data);
    }).catch((err) => {
      reject(err);
    });
  });
}

function saveUser(callback, user) {
  return new Promise((resolve, reject) => {
    console.log('1. saving...');
    setTimeout(() => {
      console.log('2. the user was saved! user name is ', user.name);
      resolve(callback(null, user));
      // reject('reason');
    }, 200);
  });
}

// main function that I need to pass the user variable into saveUser() function
let user = {name: 'Rick'};
init(saveUser, null, user).
  then(() => console.log('3. Promise finished with success!')).
  catch((err) => console.log('3. Promise was rejected!', err));

＆＃13;

如果您不想为此创建新的fn，您甚至可以在某处保存第一个解析器/拒绝器，或者在调用时将其传递给Promise。

Answer 3

init(cb => saveUser(cb, user))

或

将saveUser(callback, user)更改为saveUser(user, callback)然后

init(saveUser.bind(this, user))

将带有回调和其他参数的函数传递给另一个函数

3 个答案: