一个一个地执行承诺

我有一个需要按顺序执行的test_func,即; first_call,second_call,third_call.

目前的输出: -

started == first_call
VM81:49 status in : first_call  pending
VM81:47 started == second_Call
VM81:47 started == third_Call
VM81:49 status in : second_Call  pending
VM81:49 status in : third_Call  pending


function test_func(call_from){
  var deferred = $.Deferred();
    console.log('started ==',call_from)
  setTimeout(function(){
    console.log("status in :",call_from + '  ' +  deferred.state());
    deferred.resolve();
  },5000);

  return deferred.promise();
};
test_func('first_call').then(function(){
    test_func('second_Call')
  }).then(function(){
    test_func('third_Call')
  })

https://jsfiddle.net/44Lm3at0/

确保您发送链中的 每个Promise下游,例如:Promisereturn

test_func('first_call')
  .then(function(){
    return test_func('second_Call');
  })
  .then(function(){
    return test_func('third_Call');
  })
  .then(function() {
     console.log('done');
   });

并看到更新的js小提琴来证明它:https: //jsfiddle.net/44Lm3at0/1/

要添加上,如果你不这样做return的Promise,在链中的每个项目将在并行(由一点点时间偏移)上运行,而不是按顺序.通过返回它们,您通知JavaScript您要"等待" Promise完成,允许链的then正常工作.