Question

我想做什么

getFoo()
  .then(doA)
  .then(doB)
  .then(function(){
    ifC().then(function(res){
    if(res) return doC();
    else return doElse();
  });

我认为代码非常明显？无论如何：

我希望在给出特定条件（也是承诺）时调用承诺。我可能会做类似

的事情

var sass = require('../sass/authenty.scss');

但这感觉非常冗长。

我正在使用bluebird作为promise库。但我想如果有类似的东西，它会在任何诺言库中都一样。

Answer 1

您不需要嵌套.then次来电，因为ifC似乎还会返回Promise：

getFoo()
  .then(doA)
  .then(doB)
  .then(ifC)
  .then(function(res) {
    if (res) return doC();
    else return doElse();
  });

你也可以预先做一些腿部工作：

function myIf( condition, ifFn, elseFn ) {
  return function() {
    if ( condition.apply(null, arguments) )
      return ifFn();
    else
      return elseFn();
  }
}

getFoo()
  .then(doA)
  .then(doB)
  .then(ifC)
  .then(myIf(function(res) {
      return !!res;
  }, doC, doElse ));

Answer 2

我认为您正在寻找类似this

的内容

您的代码示例：

getFoo()
  .then(doA)
  .then(doB)
  .then(condition ? doC() : doElse());

必须在开始链之前定义条件中的元素。

Answer 3

基于Using the Dialog APIs in an authentication flow，这是我想出的可选项：

注意：如果您的条件函数确实需要作出承诺，请查看@ TbWill4321的答案

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then()

来自@jacksmirk的条件 getFoo() .then(doA) .then(doB) .then((b) => { ifC(b) ? doC(b) : Promise.resolve(b) }) // to be able to skip doC() .then(doElse) // doElse will run if all the previous resolves

的答案得到改善

then()

编辑：我建议你看一下蓝鸟关于getFoo() .then(doA) .then(doB) .then((b) => { ifC(b) ? doC(b) : doElse(b) }); // will execute either doC() or doElse() this other question
的讨论

条件然后在承诺（蓝鸟）

3 个答案: