javascript - TypeScript es6-promise，我如何匹配 Promise 构造函数

Question

试试这个:

  init():Promise<mongodb.Db> {
    return new Promise<mongodb.Db>((resolve : (value?: R | Thenable<R>) => void, reject: (error?: any) => void) => {
      this.db = new mongodb.Db("test", new mongodb.Server("localhost", 12017));

      this.db.open((err, db) => {
        if (err) {
          reject(err);
        } else {
          resolve(db);
        }
      });
    });
  }

给我这个:

error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.

我做错了什么？我直接从 Promise 的类定义中复制的构造函数参数。尝试了很多很多不同的方法来做到这一点，但都没有奏效。显然，因此问题 :)

Answer 1

不确定您从哪里得到这个定义。 您的编译器目标是否设置为 es6 ？

来自 lib.es6.d.ts

/**
 * Creates a new Promise.
 * @param executor A callback used to initialize the promise. This callback is passed two arguments: 
 * a resolve callback used resolve the promise with a value or the result of another promise, 
 * and a reject callback used to reject the promise with a provided reason or error.
 */
new <T>(executor: (resolve: (value?: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void): Promise<T>;

适合我的 typescript 1.7.5，目标 es6

这应该适合你

return new Promise<mongodb.Db>((resolve: (value?: any) => void, reject: (reason?: any) => void) => {
...
 })