typescript 如何创建从回调函数返回承诺的函数
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How to create function that return promise from callback function
提问by user1084081
I use javascript library that has api.
我使用具有 api 的 javascript 库。
libapi.callnetwork(arg1,callback(data){
//handle data
}
then i create service function to call api like this
然后我创建服务函数来像这样调用 api
myFunction():Promise<any>{
libapi.callnetwork(arg1,callback(data){
return new Promise(resolve=>resolve(data));
})
}
myFunction will get error because it must return promise or declare as void. How can i create function that return promise from this api?
myFunction 会出错，因为它必须返回 promise 或声明为 void。我如何创建从这个 api 返回承诺的函数？
回答by Bergi
The idea is not to create and return the promise from inside the callback, but to create it in the outside function (where you can returnit) and only resolvethe promise from the callback:
这个想法不是从回调内部创建和返回承诺，而是在外部函数中创建它（在你可以的return地方）并且只从回调中解析承诺：
myFunction():Promise<any>{
return new Promise(resolve => {
libapi.callnetwork(arg1, callback(data){
resolve(data);
});
});
}
or simply
或者干脆
myFunction():Promise<any>{
return new Promise(resolve => {
libapi.callnetwork(arg1, resolve);
});
}
回答by Paul S.
Vanilla, grab the resolve function
香草，抓住解析功能
let myFunction = () => {
let resolve;
let promise = new Promise(r => resolve = r);
libapi.callnetwork(arg1, resolve);
return promise;
};
回答by Meir
myFunction():Promise<any>{
let resolveFn = (data) => data;
libapi.callnetwork(arg1, resolveFn);
return new Promise(resolveFn);
}
