gskachkov

const promise = new Promise(resolve => {
  setTimeout(()=>resolve('success'));
});

const startOperation = () => { console.log('start'); };
const finishOperation = () => { console.log('finish'); };

startOperation();

promise

gskachkov

const promise = new Promise(resolve => {
  setTimeout(()=>resolve('success'));
});

const startOperation = () => { console.log('start'); };
const finishOperation = () => { console.log('finish'); };

startOperation();

promise

gskachkov

Promise.reject('error #1')
  .then(value => console.log('level-1:', value), error => console.log('level-1-error:', error))
  .catch(error => console.log('error in catch:', error))
  .finally(() => console.log('finally'))
  .then(value => console.log('level-2:', value), error => console.log('level-2-error:', value));

// level-1-error: error #1
// finally
// level-2: undefined

gskachkov

Promise.reject('reject')
  .finally(() => console.log('finally#1'))
  .catch(error => console.log('catch#1', error))
  .catch(error => console.log('catch#2', error));
//finally#1
//catch#1 reject

Promise.resolve('resolve')
  .then(result=> { console.log('then#1', result); return Promise.resolve('next-step'); })
  .finally(() => console.log('finally#1'))

gskachkov

var weaver =  function (target, methodName) {
  var before = function () { 
    console.log(arguments);
  };
  
  var old = target[methodName];
  target[methodName] = function () {
    before.apply(this, arguments);
    return old.apply(this, arguments);
  };

gskachkov

var proxiedObject = new Proxy(target, handler);

gskachkov

const handler = {
  defineProperty: function(target, property, descriptor) {
    if (property.charAt(0) === "_") return false; 
    return Reflect.defineProperty(target, property, descriptor);
  }
};

const proxy = new Proxy({}, handler);

proxy.id = "ABCD"; // { id: 'ABCD' } 

gskachkov

const handler = {
  get: function(target, property, receiver) {
    if (property.startAt(0) === "_") return undefined; 
    return target[property];
  }
};

const proxy = new Proxy({}, handler);

console.log(proxy.id); // 'ABCD'

gskachkov

class A {  
  constructor (value) { this.value = value; }
  getValue() { return this.value; } 
}

const proxiedClass = new Proxy(A, {
  construct: function(target, [ first ], newTarget) {
     return new target(first + ":proxy-value");
  }
});

gskachkov

const foo = (a, b, c) => `${a}:${b}:${c}`;

const proxy = new Proxy(foo, {
  apply: function(target, thisArg, argumentsList) {
    return target.apply(thisArg, argumentsList);
  }
});

console.log(proxy("1", "2", "3")); // 1:2:3