Question

我正在编辑TypeScript文件，TypeScript编译器或Visual Studio代码中找不到Promise。取而代之的是PromiseConstructorLike, PromiseLike<T>，如下面的lib.d.ts或lib.es6.d.ts所示。

declare type PromiseConstructorLike = new <T>(executor: (resolve: (value?: T | PromiseLike<T>) => void, reject: (reason?: any) => void)
=> void) => PromiseLike<T>;

interface PromiseLike<T> {
    /**
    * Attaches callbacks for the resolution and/or rejection of the Promise.
    * @param onfulfilled The callback to execute when the Promise is resolved.
    * @param onrejected The callback to execute when the Promise is rejected.
    * @returns A Promise for the completion of which ever callback is executed.
    */
    then<TResult>(onfulfilled?: (value: T) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => TResult | PromiseLike<TResult>): PromiseLike<TResult>;
    then<TResult>(onfulfilled?: (value: T) => TResult | PromiseLike<TResult>,

我尝试将以下内容放入我的TypeScript文件

中

var Promise : PromiseConstructorLike;
...

new Promise(function (resolve, reject) {
    ...
    return value;

}).then(value => {
    ...
});

编译，但是我得到运行时错误

TypeError: Promise is not a constructor

如上所示，完成new Promise(的正确语法或代码是什么？

Answer 1

declare var Promise : PromiseConstructorLike;

Answer 2

自编译编解码器以来，这似乎不是类型声明的问题。你需要让你在JS运行时实际拥有Promise。这可以通过使用promise polyfill来实现。

Answer 3

增加一行

declare var Promise : PromiseConstructorLike;

你可以在Typescript中使用Promise，如下所示：

let myPromise= new Promise((resolve,reject) =>{...});

声明类型为PromiseConstructorLike，TypeScript中的新Promise

3 个答案: