js 承诺等到解决后再继续 "main"

Question

如何在 JavaScript

中使用函数之前强制函数解决未决承诺

  generateKey(pass, iter).then(function(result) {
    Pkey = result;
  });

上面的 Pkey returns <empty string> 在解决之前我可以写一个循环来检查非空但这似乎违反直觉，不是吗？

和

  Pkey = generateKey(pass, iter);

returns 最终实现的未决承诺

function generateKey(passwd, iterations) {

  var encoder = new TextEncoder('utf-8');
  var passphraseKey = encoder.encode(passwd);
  var saltBuffer = encoder.encode("carthage");

  return crypto.subtle.importKey(
    'raw',
    passphraseKey,
    {name: 'PBKDF2'},
    false,
    ['deriveBits', 'deriveKey']
  ).then(function(key) {
//    console.log(key);
    return window.crypto.subtle.deriveKey(
    { "name": 'PBKDF2',
      "salt": saltBuffer,
      "iterations": iterations,
      "hash": 'SHA-256'
    },
    key,
    { "name": 'AES-CBC',
      "length": 256
    },
    true,
    [ "encrypt", "decrypt" ]
  )
  }).then(function (webKey) {
//    console.log(webKey);
    return crypto.subtle.exportKey("raw", webKey);
  }).then(function (buffer) {
//    console.log(buffer);
//    console.log(saltBuffer);
//    console.log("Private Key = " + buf2hex(buffer));
//    console.log("Salt = " + bytesToHexString(saltBuffer));
    return buffer;
  });

}



function buf2hex(buffer) { // buffer is an ArrayBuffer
  return Array.prototype.map.call(new Uint8Array(buffer), x => ('00' + x.toString(16)).slice(-2)).join('');
}



function bytesToHexString(byteArray) {
  return Array.prototype.map.call(byteArray, function(byte) {
    return ('0' + (byte & 0xFF).toString(16)).slice(-2);
  }).join('');
}

Answer 1

您可以使用async & await如下

async function generateKey(passwd, iterations) {...}
...
Pkey = await generateKey(pass, iter);

js 承诺等到解决后再继续 "main"

js promise wait until resolved to continue "main"

javascript

asynchronous

promise