嵌套异步回调

  1. function double(value, success, failure) {
  2.   setTimeout(() => {
  3.     try {
  4.       if (typeof value !== 'number') {
  5.         throw 'Must provide number as first argument';
  6.       }
  7.       success(2 * value);
  8.     } catch (e) {
  9.       failure(e);
  10.     }
  11.   }, 1000);
  12. }
  14. const successCallback = (x) => {
  15.   double(x, (y) => console.log(`Success: ${y}`));
  16. };
  17. const failureCallback = (e) => console.log(`Failure: ${e}`);
  19. double(3, successCallback, failureCallback);
  21. // Success: 12 (printed after roughly 1000ms)
  22. //NestingAsyncCallbacksExample01.js

异步返回值

  1. function double(value, callback) {
  2.   setTimeout(() => callback(value * 2), 1000);
  3. }
  5. double(3, (x) => console.log(`I was given: ${x}`));
  6. // I was given: 6 (printed after roughly 1000ms)