promise.js

// n秒経ったらresolve
var delay = function(second) {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve(second)
    }, 1000 * second)
  })
}
delay(2).then(function(n) {
  console.log(n)
})

// Promise#catch
new Promise(function() {
  throw new Error(1)
}).catch(function(a) {
  console.log(a)
})

new Promise(function(resolve, reject) {
  reject(2)
}).catch(function(a) {
  console.log(a)
})

// resolveにpromiseを渡すとrejectされる (Firefox 32だと正しく動作しない)
(function() {
var p = new Promise(function(resolve, reject) {
  setTimeout(function() {
    console.log(p)
    resolve(p)
  })
})
p.then(function() {
  console.log('resolved')
}, function() {
  console.log('rejected')
})
})()

// Promise.all
Promise.all([delay(2), delay(3)]).then(function(n) {
  console.log(n)
})

// Promise.race
Promise.race([delay(2), delay(3)]).then(function(n) {
  console.log(n)
})

// Promise.reject
Promise.reject(delay(2)).then(function() {
  console.log('resolved')
}, function() {
  console.log('rejected')
})

// Promise.resolve
Promise.resolve(delay(2)).then(function() {
  console.log('resolved')
}, function() {
  console.log('rejected')
})