Using callback function inside array.map javascrip

问题:

I am trying to bcrypt password for every user in an array.

router.post("/insertuser", (req, res) => {

  var promises = users.map((item) => {

    bcrypt.genSalt(10)
      .then((salt) => {
        return item
      })    
  })

  Promise.all(promises)
    .then((results) => {
      console.log(results)
      res.json({
        "data": results
      })
    })    
})//end route

But I am getting results = [undefined,undefined].

How can I return array element from bcrypt.genSalt(10).then

Please help as I am new to ES6

EDIT: My user users array is like this:

[{ "username": "admin", "admin": true} ]

回答1:

Simply return the promise from bcrypt.genSalt.

router.post("/insertuser", (req, res) => {

  var promises = users.map((item) => {

    return bcrypt.genSalt(10)
      .then((salt) => {
        return item
      })    
  })

  Promise.all(promises)
    .then((results) => {
      console.log(results)
      res.json({
        "data": results
      })
    })    
})//end route

回答2:

When you add .then() after any promise it will directly get resolved. In your code users.map() will run synchronously and the promises will have undefined. Here is the code you can use :

router.post("/insertuser", (req, res) => {
    var promises = users.map((item) => {
      return bcrypt.genSalt(10);
    })

    Promise.all(promises)
      .then((results) => {
        console.log(results)
    });  
})//

Also notice that salt is used to generate hash. You are only generating salt. To generate hash of password also add bcrypt.hash(password,salt). Here is the code :

var promises = users.map((item) => {
  return bcrypt.genSalt(10);
})

Promise.all(promises)
  .then((results) => {
    promises = results.map((item, index) => {
      return bcrypt.hash(users[index], item);
    });
    return Promise.all(promises);
  })
  .then(result => {
    console.log(result);
  })
  .catch(err => {
    console.log(err);
  });