function callback() {
 console.log('Done');
}
console.log('before setTimeout()');
setTimeout(callback, 1000); // 1秒钟后调用callback函数
console.log('after setTimeout()');

request.onreadystatechange = function () {
 if (request.readyState === 4) {
  if (request.status === 200) {
   return success(request.responseText);
  } else {
   return fail(request.status);
  }
 }
}

var ajax = ajaxGet('http://...');
ajax.ifSuccess(success)
 .ifFail(fail);

'use strict';

new Promise(function () {});
// 直接运行测试:
alert('支持Promise!');

function test(resolve, reject) {
 var timeOut = Math.random() * 2;
 log('set timeout to: ' + timeOut + ' seconds.');
 setTimeout(function () {
  if (timeOut < 1) {
   log('call resolve()...');
   resolve('200 OK');
  }
  else {
   log('call reject()...');
   reject('timeout in ' + timeOut + ' seconds.');
  }
 }, timeOut * 1000);
}

var p1 = new Promise(test);
var p2 = p1.then(function (result) {
 console.log('成功：' + result);
});
var p3 = p2.catch(function (reason) {
 console.log('失败：' + reason);
});

// 如果成功，执行这个函数：
p1.then(function (result) {
 console.log('成功：' + result);
});

p2.catch(function (reason) {
 console.log('失败：' + reason);
});

new Promise(test).then(function (result) {
 console.log('成功：' + result);
}).catch(function (reason) {
 console.log('失败：' + reason);
});

'use strict';

// 清除log:
var logging = document.getElementById('test-promise-log');
while (logging.children.length > 1) {
 logging.removeChild(logging.children[logging.children.length - 1]);
}

// 输出log到页面:
function log(s) {
 var p = document.createElement('p');
 p.innerHTML = s;
 logging.appendChild(p);
}
new Promise(function (resolve, reject) {
 log('start new Promise...');
 var timeOut = Math.random() * 2;
 log('set timeout to: ' + timeOut + ' seconds.');
 setTimeout(function () {
  if (timeOut < 1) {
   log('call resolve()...');
   resolve('200 OK');
  }
  else {
   log('call reject()...');
   reject('timeout in ' + timeOut + ' seconds.');
  }
 }, timeOut * 1000);
}).then(function (r) {
 log('Done: ' + r);
}).catch(function (reason) {
 log('Failed: ' + reason);
});

job1.then(job2).then(job3).catch(handleError);

'use strict';

var logging = document.getElementById('test-promise2-log');
while (logging.children.length > 1) {
 logging.removeChild(logging.children[logging.children.length - 1]);
}

function log(s) {
 var p = document.createElement('p');
 p.innerHTML = s;
 logging.appendChild(p);
}
// 0.5秒后返回input*input的计算结果:
function multiply(input) {
 return new Promise(function (resolve, reject) {
  log('calculating ' + input + ' x ' + input + '...');
  setTimeout(resolve, 500, input * input);
 });
}

// 0.5秒后返回input+input的计算结果:
function add(input) {
 return new Promise(function (resolve, reject) {
  log('calculating ' + input + ' + ' + input + '...');
  setTimeout(resolve, 500, input + input);
 });
}

var p = new Promise(function (resolve, reject) {
 log('start new Promise...');
 resolve(123);
});

p.then(multiply)
 .then(add)
 .then(multiply)
 .then(add)
 .then(function (result) {
 log('Got value: ' + result);
});

'use strict';

// ajax函数将返回Promise对象:
function ajax(method, url, data) {
 var request = new XMLHttpRequest();
 return new Promise(function (resolve, reject) {
  request.onreadystatechange = function () {
   if (request.readyState === 4) {
    if (request.status === 200) {
     resolve(request.responseText);
    } else {
     reject(request.status);
    }
   }
  };
  request.open(method, url);
  request.send(data);
 });
}
var log = document.getElementById('test-promise-ajax-result');
var p = ajax('GET', '/api/categories');
p.then(function (text) { // 如果AJAX成功，获得响应内容
 log.innerText = text;
}).catch(function (status) { // 如果AJAX失败，获得响应代码
 log.innerText = 'ERROR: ' + status;
});

var p1 = new Promise(function (resolve, reject) {
 setTimeout(resolve, 500, 'P1');
});
var p2 = new Promise(function (resolve, reject) {
 setTimeout(resolve, 600, 'P2');
});
// 同时执行p1和p2，并在它们都完成后执行then:
Promise.all([p1, p2]).then(function (results) {
 console.log(results); // 获得一个Array: ['P1', 'P2']
});

var p1 = new Promise(function (resolve, reject) {
 setTimeout(resolve, 500, 'P1');
});
var p2 = new Promise(function (resolve, reject) {
 setTimeout(resolve, 600, 'P2');
});
Promise.race([p1, p2]).then(function (result) {
 console.log(result); // 'P1'
});