20190429 - Promise链

[onvno]

Promise链

Promises chaining

new Promise(function(resolve, reject) {

  setTimeout(() => resolve(1), 1000);

}).then(function(result) {

  alert(result); // 1

  return new Promise((resolve, reject) => { // (*)
    setTimeout(() => resolve(result * 2), 1000);
  });

}).then(function(result) { // (**)

  alert(result); // 2

  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(result * 2), 1000);
  });

}).then(function(result) {

  alert(result); // 4

});

Promise All Request

Promise All with Axios

let URL1 = "https://www.something.com"
let URL2 = "https://www.something1.com"
let URL3 = "https://www.something2.com"

const promise1 = axios.get(URL1);
const promise2 = axios.get(URL2);
const promise3 = axios.get(URL3);

Promise.all([promise1, promise2, promise3]).then(function(values) {
  console.log(values);
});

or

var promise1 = Promise.resolve(3);
var promise2 = 42;
var promise3 = new Promise(function(resolve, reject) {
  setTimeout(resolve, 100, 'foo');
});

Promise.all([promise1, promise2, promise3]).then(function(values) {
  console.log(values);
});
// expected output: Array [3, 42, "foo"]