gskachkov

async function foo () {
  const result = await fetch("https://randomuser.me/api/?results=10", { method: "GET" }); 
  return result;
}

async function bar() {
  console.log(await foo()); 
};

bar();

gskachkov

• Overview of nonlinear control flow in javascript
• Async function
  • Syntax(function, method, async arrow function expression)
  • Runtime -> Diagram how it works…
  • Examples
  • Use Symbols.Async
• Using await
• Using promises
  • Promise all
• Promise race

gskachkov

var getPromise = (value, delay) => {
  return new Promise(resolve => {
    setTimeout(() => resolve(value), delay);
  });
};

var promise1 = getPromise('value-1', 350);
var promise2 = getPromise('value-2', 250);
var promise3 = getPromise('value-3', 150);

gskachkov

var getPromise = (value, delay) => {
  return new Promise(resolve => {
    setTimeout(() => resolve(value), delay);
  });
};

var promise1 = getPromise('value-1', 150);
var promise2 = getPromise('value-2', 250);
var promise3 = getPromise('value-3', 50);

gskachkov

var promiseImmediate = Promise.reject('Immediate value');
promiseImmediate.then(
  result => console.log('promiseImmediate success:', result), 
  error => console.log('promiseImmediate fail:', error)
); // promiseImmediate fail: Immediate value

promiseImmediate.catch(error => console.log('promiseImmediate catch:', error));

var resolver = {};
var promise = new Promise((resolve, reject) => { resolver.reject = reject; });

gskachkov

var promiseImmediate = Promise.resolve('Immediate value');
promiseImmediate.then(result => console.log('promiseImmediate:', result)); 
// 'promiseImmediate: Immediate value' will visible imidiatly 

var resolver = {};
var promise = new Promise(resolve => { resolver.resolve = resolve; });

var promiseDefferred = Promise.resolve(promise);
promiseDefferred.then(result => console.log('promiseDefferred:', result)); 
// No any text

gskachkov

var getPromise = (value, delay) => {
  return new Promise(resolve => {
    setTimeout(() => resolve(value), delay);
  });
};

var promise = getPromise('start value', 150);

promise
.then(result => {

gskachkov

var bar = new Promise(function (resolve) {
  setTimeout(function () { reject('error'); }, 50);
});

bar.then(function() {}, function (reject) { 
  console.log('reject:', reject); 
}); // reject:error

bar.catch(function (reject) { 
  console.log('catch:', reject); 

gskachkov

// Create promise
var promise = new Promise(function (resolve) {
  //Resolve promise in 50ms with string 'success'
  setTimeout(function () { resolve('success'); }, 50);
});

// Handle successful resolve of promise
promise.then(function (result) { 
  console.log(result); // Print: success
});

gskachkov

var promise = new Promise(function(resolve, reject) { … } );