如何将参数传递给 promise function

Question

this might seem a silly question but I am a newbie in this topic. I am working on promises on node js. And I want to pass parameter to a promise function. However I could not figure it out.

someModule.someFunction.then(username, password,function(uid) {
  /*stuff */
}

and the function is something like

var someFunction = new Promise(username, password, function(resolve, reject) {
  /*stuff using username, password*/
  if ( /* everything turned out fine */ ) {
    resolve("Stuff worked!");
  } else {
    reject(Error("It broke"));
  }
});

Answer 1

Wrap your Promise inside a function or it will start to do its job right away. Plus, you can pass parameters to the function:

var some_function = function(username, password)
{
 return new Promise(function(resolve, reject)
 {
  /*stuff using username, password*/
  if ( /* everything turned out fine */ )
  {
   resolve("Stuff worked!");
  }
  else
  {
   reject(Error("It broke"));
  }
 });
}

Then, use it:

some_module.some_function(username, password).then(function(uid)
{
 // stuff
})

ES6:

const some_function = (username, password) =>
{
 return new Promise((resolve, reject) =>
 {
  /*stuff using username, password*/

  if ( /* everything turned out fine */ )
  {
   resolve("Stuff worked!");
  }
  else
  {
   reject(Error("It broke"));
  }
 });
};

Use:

some_module.some_function(username, password).then(uid =>
{
 // stuff
});

Answer 2

Another way( Must Try ):

 var promise1 = new Promise(function(resolve, reject) { resolve('Success!'); }); var extraData = 'ImExtraData'; promise1.then(function(value) { console.log(value, extraData); // expected output: "Success!" "ImExtraData" }, extraData);

Answer 3

Even shorter

var foo = (user, pass) =>
  new Promise((resolve, reject) => {
    if (/* condition */) {
      resolve("Fine");
    } else {
      reject("Error message");
    }
  });

foo(user, pass).then(result => {
  /* process */
});

Answer 4

Not sure if understand correctly but in order to send argument from promise to another function you can do something like this:

 function logUser(username, password){ return new Promise((resolve, reject) => { let response = 'user logged in' resolve(response) }) } function showMessage(msg){ console.log(msg) } logUser('user', 'pass').then((respFromLogUser) => { showMessage(respFromLogUser) })

Answer 5

You can use .bind() to pass the param( this ) to the function.

var someFunction =function(resolve, reject) {
  /* get username, password*/
  var username=this.username;
  var password=this.password;
  if ( /* everything turned out fine */ ) {
    resolve("Stuff worked!");
  } else {
    reject(Error("It broke"));
  }
}
var promise=new Promise(someFunction.bind({username:"your username",password:"your password"}));

Answer 6

I know this is old, but this may help someone digging through google. This is a more practical example where I just pass 2 parameters to a promise function and wait for it to resolve. Hopefully this helps. The setTimeout simulates "processing time". After 3 seconds the value will be returned from the promise and printed to screen.

const addNumbers = (a, b) => {
    
  return new Promise((resolve, reject) => {
    
    setTimeout(() => {
      resolve(a + b);
    }, 3000);
  
  });
  
  
};

let getResult = async (a, b) => {
    let value = await addNumbers(a, b);
    console.log(value);
};

getResult(1, 3);

Answer 7

You can return your promise in a function with arguments. Like this:

function someFunction(username, password) {
      return new Promise((resolve, reject) => {
        // Do something with the params username and password...
        if ( /* everything turned out fine */ ) {
          resolve("Stuff worked!");
        } else {
          reject(Error("It didn't work!"));
        }
      });
    }
    
    someFunction(username, password)
      .then((result) => {
        // Do something...
      })
      .catch((err) => {
        // Handle the error...
      });

Answer 8

i use this..

let verifyEmail = (email) => new Promise((resolve, rejected) => {
    let rsp = {isRepeated:false}
    let sql = `select id from users where email='${email}' `
    try{
        db.query(sql, (err,result)=>{
            if(!err){
                if(result.length > 0){
                    rsp = {isRepeated:true}
                }
            }
        })
        resolve(rsp)
    }catch(e){
        rejected({ok:false,err:e})
    }
})