javascript - 如何正确使用 promise/deferred 模式

Question

我正在尝试链接两个函数 test1 和 test2，它们需要在调用第三个函数之前完成(首先是 test1，然后是 test2)。我在 jquery 中应用 promise/deferred 模式时遇到了问题。谁能帮忙？

function test1(){
    setTimeout(function() {
        console.log("test1");
        return 1;
    }, 10000);
}

function test2(){
    setTimeout(function() {
        console.log("test2");
        return 2;
    }, 10000);
}


var promise1 = test1().promise();
var promise2 = test2().promise();

when(
    promise1,
    promise2
).then(function(a,b) {
    console.log("test1 and test2 done");
});

Answer 1

您还没有在代码中使用任何 promise 框架...

一种方法是使用 jQuery Deferred()喜欢

function test1() {
  //create a deferred object
  var deferred = $.Deferred()
  setTimeout(function() {
    //once the taks is completed mark the promise as resolved
    deferred.resolve(1);
  }, 2000);
  //return the promise object
  return deferred.promise();
}

function test2() { //create a deferred object
  var deferred = $.Deferred()
  setTimeout(function() {
    //once the taks is completed mark the promise as resolved
    deferred.resolve(2);
  }, 1000); //return the promise object
  return deferred.promise();
}


var promise1 = test1();
var promise2 = test2();

$.when(promise1, promise2).then(function(a, b) {
  console.log("test1 and test2 done", a, b);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>

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其他可能的 promise 解决方案是

• > html5 promise
• > Q
• > rsvp