javascript - promise : How to pass data?

Question

我想了解 promises 是如何运作的。我看到它就像一个“链式回调”……或多或少……但是……可以将您获得的值提取到外部值/数组/对象吗？

Promise1()
  .then(return x)
  .then()
  .then()
  .then(function(x){
    console.log(x);
  });

我如何将数据从第一个 .then() 传递到第四个 .then()？

任何帮助我理解 promise 的努力都将不胜感激。

Answer 1

你可以做到，但你需要将 x 值从一个 then 传递给另一个:

Promise1()
    .then(function() {
        return x; // The "x" is wrapped in a resolved promise by "then method"
    })
    .then(function(x) { // The "then" pass to the fulfillment callback the value inside the promise taken in input, which is the "x" value
        return x; //Same as above, we return the "x" value to pass it to the next "then" function
    })
    .then(function(x) { // Same as above
        return x; // Same as above
    })
    .then(function (x) { 
        console.log(x); // Here you can access the "x" value and print it
    })